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BIOLOGICAL AND EMBRYOLOGICAL STUDIES 
x ON FORMICIDAE 


3 
BY 


4 


MAURICE COLE TANQUARY 


A. B., University of Illinois, 1907 
A.M.., University of Illinois, 1908 


THESIS 
Submitted in Partial Fulfilment of the Requirements for the 
Degree of 
DOCTOR OF PHILOSOPHY 
IN ENTOMOLOGY 
IN 
THE GRADUATE SCHOOL 
OF THE 


UNIVERSITY OF ILLINOIS 


Po 12 


CONTENTS — 


PAGE 
INGO WA dati ONES yore aie: aet vsee res ee casera oleae Abe Sieh k Sle eel oe era eet eee eee 3 
Biological? Stadt es) sp velne cis vseacties eke bese orel oth os Sik Ta Soe lees eae er a 5 
I. The life history of the corn-field ant, Lasius niger var. americanus Emery 5 
IMetHO US: aivans't Wook ARIA: ice reese here acre tet sts leas er 5 
Nipbial: flights) cckisyeget ise deseo fateeea eect deter Berens oltnce(e, SRO eve reesc ace 5 
Founding: of ‘thescolony s-2..b ace ane ee eee ee ne ee es = ys 7 
Enibernation, ..6.G.2cks aoe ee ee EE eee pte eee eee e ee eeee 24 
SS UEVATTLATY. 1-5 layin: nevoaw oye eb Sia ora ey CYA CIID OORT Re PT REN eee. oo cee ECT SV ce 28 
Additional-nOtes ” 42.4 eee ea me iete aie) Ei in Par AN pi 20 
II. Experiments on the trail formation and orientation of the common house 
hale VOM O Lo pve AOMIS. Mg bog 6G000bb ako oUUGOadK OOcOsbsG0nO> 31 
Additional, arotesy eee ers ate eae eae erotic srolie tio atees ot eee aoe 40 
GOmElUSiOMs i tee ER Cees eR eRe ato tecas rea cen eve Ta negra MEME Ont 41 
Embryological «Studies severe ame eeer cree cistcitieds s ceteinvas atusre ee eves eens eee 42 
Studies on the embryology of Camponotus herculeanus var. ferrugineus 
Fabr. and Myrmica scabrinodis var. sabuleti Meinert............. 42 
Method sires seit sean ere eee eee ete et ess So, 0, Sievsltochs dis ies trav euicvavarioes cnet Sei tate 42 
il DB naar tod emer ar oho clei dlsinia di cid  Kitid-0 GIO AER ea PRES ROCIO Ho. cas 01.0,0 43 
Formation otgthemblasto cd eginteere retest: oral alorsve)-r-etave siete) vee rereterererene 47 
The developmentson the Extenital TOL. 3. 6X6 + seers o1c.6 0:0 oie elcieteleroineiete 56 
The development of the external form of the embryo of Myrmica.... 59 
WesiereeN uly Kel 10 OR i) Sa. Oo th ee a pe raeE en mre Croce Gio dc 64 
Explanation :of- plates. <tecasevncpeteee e eercectintoe Beeianes ls osc a rehey acer rept open 69 


SVG i ae Re eS I MONA EY ht) aka et ie nee EE a aM Rtn te oa nicae 4 


N3L.MA 


ACKNOWLEDGMENTS 


3 N 


The studies upon which this thesis is based have been prosecuted 
under the direction of Professor S. A. Forbes and Professor J. W. 
Folsom, the “Biological Studies” having been carried on under the 
direction of the former and the “Embryological Studies” under the di- 
rection of the latter. To both Professor Forbes and Professor Folsom, 
my sincerest thanks are due for their advice, encouragement, and as- 
sistance throughout the progress of the work. I wish also to acknowl- 
edge the aid of Mr. W. C. Matthews and Mr. Alvah Peterson in the 
preparation of the drawings. 


{RARY 
‘bANA-CHAMPAIGN 


VITA 


The writer was born at Lawrenceville, Illinois, November 26, 188r. 
He attended the public schools of Lawrenceville, and in 1899 entered 
Vincennes University, from which he was graduated in 1903. He 
taught for four years in the public schools of Lawrence county, IIli- 
nois. He entered the University of [linois in 1905, served for three 
semesters as undergraduate assistant in General Zoology, and was 
graduated in 1907. He then entered the Graduate School of the Uni- 
versity of Illinois and received the degree of master of arts in 1908. 
In 1908-1909 he was for half his time assistant to the State Ento- 
mologist of Illinois and a laboratory assistant in Vertebrate Embry- 
ology. From 1909 to 1912 he was half-time assistant in Entomology 
in the University of Illinois. During the summer of 1910 he studied 
in Harvard University, and during the summer of 1911, he was Field 
Agent for the State Entomologist of Minnesota. He has published a 
paper in the April number of the Biological Bulletin for rg11, on “Ex- 
periments on the Adoption of Lasius, Formica, and Polyergus Queens 
by Colonies of Alien Species,” and one in the Transactions of the 
Mlinois State Academy of Science for 1911, on “A preliminary List 
of the Ants of [linois.” 


BIOLOGICAL STUDIES 


I. THe Lire History oF THE CORN-FIELD ANT, 
Lasius miger var. americanus Emery 


Although the common corn-field ant, Lastus niger var. americanus 
Emery, is said to be the most abundant of all North American insects, 
its complete life history has never been worked out. The most that 
we have on the subject is given in Bulletin 131 of the Illinois Experi- 
ment Station by Forbes. He there reports that in four cases the first 
eggs from young queens were obtained May 8, 9, 10, and 15; that the 
egg periods were 16, 17, 19, and 23 days; that the pupal stage aver- 
aged about 18 days; and that the total number of young produced by 
a single female in the first year was in three cases 8, 9, and 19 work- 
ers. The more extensive data which I have been able to obtain cor- 
respond in great measure to those just given. 


METHODS 


The method followed in this life history study consisted (1) in 
making observations in the field at all times of the year, (2) in mak- 
ing daily observations on young fertilized and isolated females through 
one season, (3) in isolating old queens from large nests and getting 
counts of the eggs they laid, and (4) in keeping large colonies in 
Fielde nests under daily observation. These young fertilized females 
were obtained in the fall just after they had descended from their 
nuptial flight, or after they had formed their cells; or they were taken 
from their cells in the spring before they had begun to lay eggs. They 
were kept for the most part in Fielde nests of the ordinary type, or 
in some cases in Barth nests. The latter are more satisfactory for 
keeping the ants under natural conditions, but with them one can not 
make as accurate observations regarding the exact number of eggs 
and young. 


NUPTIAL FLIGHTS 


The nuptial flights of Lasius americanus usually occur from Au- 
gust to September. The date of a flight mentioned by Forbes is 
September 14. The earliest date for which I have positive evidence 
of a flight is September 5. I have noticed, however, in a summer’s 


6 


collecting, that during August the percentage of nests containing 
winged forms decreases, so that it is very probable that the flights 
begin during that month in this latitude. September 5, 1g10, I found © 
a large number of young dealated females of Lasius niger americanus 
crawling on the ground in a park in Boston, Mass. ‘This was about 
five o'clock in the evening. They had all removed their wings, and 
were crawling around in search of a place to burrow. A number were 
already beginning their burrows. At one place I saw six beginning 
to burrow in the same place. There were also many males flying in 
the air or crawling about, but I saw no couples in copula. The same 
afternoon I found five young dealated queens of L. latipes Walsh, a 
number of winged and dealated females of Solenopsis molesta Say, 
also a few dead males of Formica fusca var. subsericea Say. ‘This 
fact indicates that weather conditions probably determine to a large 
extent the time of a flight. ‘There had been a heavy rain the day 
before, but on that day it was clear and very warm. ‘The following 
day, September 6, with the same weather conditions, I found a large 
number of males and winged females of Cremastogaster lineolata Say 
crawling about on the walks, and two days later I saw a large number 
of Solenopsis molesta flying, many of them im copula. September 19, 
Ig10, and on almost every day for the next ten days, I caught winged 
females of Lasius niger americanus flying or saw the young queens 
crawling over the ground. On the evening of October 4, I found five 
winged and sixteen dealated queens of L. niger americanus crawling 
on the ground, one dealated queen October 11, and one October 18. 
The fact that dealated queens of this species are found crawling about 
is evidence that there has been a flight, since these queens begin to 
burrow immediately after descending from their flight and do not 
come to the surface again. 

The dates upon which I have actually witnessed the flights of 
L. americanus from the nest are September 9, September 20, and 
September 18. All the flights of this species I have noticed have been 
between 3 p. m. and 6 p. m. The best observations were obtained 
from the one of September 20. In this case the entrance of a large 
nest was near the edge of a cement walk. At 4:30 p. m. my attention 
was called to the fact that a very large number of ants were crawling 
over the walk and grass near the opening. Closer examination showed 
that there were many males, winged females, and workers there, all 
running about excitedly, and that every few minutes a male or female 
rose from the blades of grass or the walk and flew away. ‘They did 
not all fly away in the same direction, but seemed to take whatever 


7 


course they were headed for. I did not see any pairs in copula either 
in the air or on the ground. In fact, I have never found a pair of 
this species in copula, and think it quite likely that fertilization takes 
place in the nest some time before the flight. 


FOUNDING OF THE COLONY 


Several methods of founding a colony are now generally recog- 
nized. ‘These methods have been designated by Wheeler (’06, pp. 34, 
35) as the typical, the redundant, and the defective. 

In the first case the female after descending from her nuptial 
flight, removes her wings and burrows into the ground or enters a 
cavity beneath the bark of a log, or the like, where she forms a small 
cell and begins to lay eggs or passes the winter and then begins to lay 
eggs. When these hatch she feeds the larvee from her own secretions. 

In the second case the female in addition to doing all that is re- 
quired in the typical method, also cultivates certain fungi for herself 
and her brood. 

The defective method Wheeler has subdivided into (1) temporary 
social parasitism, (2) permanent social parasitism, and (3) dulosis, 
or slavery. In temporary social parasitism the female enters a queen- 
less colony of some other species and becomes adopted, thus getting 
the alien ants to rear her first brood. These alien ants naturally die 
off in the course of time, leaving a pure colony of the same species 
as the queen. 

It is very well known that the first method mentioned is the one 
usually employed by L. niger americanus, and it is generally believed 
to be the only one employed. One may find solitary females in their 
cells a few inches beneath the surface of the ground in October and 
November; and may also find late in the summer or in the spring a 
colony consisting of a queen and a few minim workers and larve, the 
product of one year’s growth. 

November 18 I found in a corn field infested with Aphis matdi- 
radicis Forbes, six separate cells, each containing a solitary female. 
There were no eggs or young. The cells were only a few inches be- 
neath the surface, three of them being beneath clods of earth. On 
April 5, I found a lone queen in her cell a few inches beneath the 
surface in a stalk-field, without eggs or young. Eggs may be laid, 
however, in the fall. On September 5, I picked up thirty-six dealated 
females that had just descended from their nuptial flights and 
placed them together in a large Fielde nest. Within the 


8 


next few days between 150 and 200 eggs were laid. These eggs, 
however, all spoiled, as though they were not properly taken care 
of. ‘This has been the case in every other instance in which I have 
had young queens lay eggs in the fall. This, however, may be due 
to artificial conditions. The queens lay again in spring, about May, 
the exact time depending upon weather conditions. The one I collected 
April 5 and kept under natural conditions laid her first egg May 16. 
Some of the queens which I kept in a warm room during the winter 
began to lay as early as the first of March. The number of young 
produced the first season is very small as compared with the number 
of eggs laid by the queen. In all my nests containing single queens, 
the queen was more or less given to eating her own eggs. Some ate 
only a few, while others ate nearly all. This was not due to lack of 
food, as I had provided food for them. The fact that all the queens 
ate their eggs to some extent, and the fact that the number of young 
produced under natural conditions is so much less than the number 
of eggs laid, lead me to believe that the queen under normal condi- 
tions eats a certain proportion of her eggs. Possibly this habit enables 
her to get the proper kind of food for her larve. 
The detailed history of a few first-year colonies follows. 


COLONY 27) 


This queen was taken November 20, from a cell which she had 
established a few inches beneath the surface of the ground in a corn 
field. The room in which she was kept during the winter was a 
greenhouse, which became quite warm (70°—8o: F.) at times; though 
at other times the temperature fell below freezing. Keeping her in a 
warm room accounts for the fact that she began laying so early. Aside 
from the fact that egg-laying began much earlier, the history of this 
colony is not different from that of others in which the queens were 
kept under natural conditions, so that these results may be taken as 
typical. 

The first egg was laid February 17. It disappeared February 22 
(probably eaten) and no other was laid until February 27, 


9 


Cotony 276* 


Date Eggs Total |} Larvze 

Feb. 27. 1 1 

ares 1 2 \ 
Mar.) 45. 1 3 

5 Dike 3 6 

* 65. 1 7 

f Sire 2 9 

arta 2 11 

eis 3: 14 

 eepa Ip) .L 15 

cae 16% 2 17 

Boe ly dy 4 21 

AS 1 22 

Seabed. . 2 24 

mines. 1 25 

oy ioe 1 26 

Be OOR: 52.3 2 28 

pee Oe. 2 30 
Apr i L:. 2 32 

Bie i 33 

ne bige 1 34 

is Gre 6 40 

- Si: 2 42 

‘ esas 4 46 

Cet lS anes 1* 45 

ne, 14. 3 48 

LS 0 47 1 

ae 3) 2 48 1 

fe Ply 5 47 6 

18 3* 41 3 

ieee 19), 1* 32 8 

oo ae P ee 0 29 3 

rire “Oat. 2 30 1 

ne ede. 5* 21 4 

Seay DEY ce 7 28 0 

ve Bei 2 30 0 

we tO 6* 24 0 

Oi bts eee 1 25 1* 

Se D9 5* 20 5* 

= 130 4* 16 0 


Total 


anne 


iit 


Pupz | Total | Adults 


Total 


*In this table the asterisk signifies missing; the dagger, accidentally injured or 


destroyed; and the double dagger, dead. 


10 


CoLtony 27b—Continued 


Total 


Ann wrwAW nrwmnwtwTFt MODaawwir- re rr KX Rh 


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an SS Se en Se AS AA A St we Sa oS oS Se Se SS 

5 * % 

= Si ferent tot Sot eel Soho Geer ISS) Te eS) fe a te ea oe eS OO eS SSS RS he! eo ee) OF = le ec | 
AY 

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fe} RNRNRQonrtnroeoaroantinnonnmnnonnonomorwnMmonoewoeododmwmrmMmwtodoec”rowmnor7nrw7Hnomecoerdsd t+ © 
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aE * * 3 % * * * * * 

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| 

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3} . Per hl ag Cte. Se ee een een UE bam mete Aree ee Ae S 

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la BAmn Hn PTT TW yFRNMNANANRMAAAAHAN HD MO | 


1g 


CoLony 27b—Continued 


w 

- 

= t+ 

= 7 To a — a — Je — oe — es — J — 2 — en — J: — 2 2 — J — Se — 2 — 2 — a — J — 2 — 2 — J — J — J —  —  —  — — —  —  — | 

< 
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an mor mArnrtntnt nnn wR DT NUNOARORMNAN BH 

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4 


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Psi WH SCHWMHWDRAEGDWOWSSOHSCSCOCORNSOMONHOSODODOCMOONSSCSSSS 
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+ DADHHHMOrmMRMDAOCNHAMNHOKFPARAOCHAHMAHMOKRAAOHAAHMOKDWOAOCH 
oS Ar NRNRQRANRNANNARN NY a mMmaMWNRNNNRANRARANR MM 
A | »w 

S 

= 

rs 


§$June 14-17, no examination made. 


12 


Cotony 27b—Concluded 


Date Eggs Total || Larve| Total Pupe | Total |} Adults| Total 
iNyofe, ALG 6 0 38 0 4 0 3 0 20 
ry Gree 0 38 0 3 il 4 0 20 
. AS. 0 38 0 3 0 3 i 21 
. Dievaiehe 0 38 0 2 1 4 0 21 
- 6 0 38 0 2 0 4 0 21 
# Mire 0 38 0 2 0 4 0 21 
" Sak 0 38 0 2 0 3 1 22 
is Opes 0 38 0 2 0 3 0 22 
we lO 8* 30 0 2 0 3 0 22 
etal 0 30 0 2 0 3 0 22 
ral il 31 0 2 0 3 0 22 
sie! 3* 28 1* 1 0 2 1 23 
Seal Sis 0 28 0 u 0 2 0 23 
SP ILC Sx. 0 28 0) i 1* i 0 23 
a, 0) 28 0 1 0 1 0 23 
a een ish 2 30 0 il 0 il 0 23 
Spbgal Orato 0 30 0 1 0 1 0 23 
Prnose 0 30 0 1 0 0 1 24 
EO He 9 38 1 2 0 0 0 24 
Sept. 1. 0 38 0 2 0 0 0 24 


I was compelled to neglect the colony for a time. September 
25, the nest contained 16 workers and 12 larve (the latter in poor 
condition) ; September 28, 5 eggs and 16 workers; and October 5, 
2 larve and 16 workers. 

This colony, consisting of the queen, 2 larvee, and 16 workers, re- 
mained the same up to November 17, when I found one of the work- 
ers dead. By November 16 the weather had become much colder, and 
during the rest of the winter the ants remained in a dormant condi- 
tion. Owing to the fact that conditions were not just right, or that 
the ants were not in the best physiological condition to enter hiberna- 
tion, the latter did not survive the winter. 

An examination of the above data shows that up to September 1, 
this queen had laid 222 eggs; that but 27 adults were reared from 
them; that but 3 adults died, one because I had injured it; that 
4 individuals died or disappeared in the pupal stage, 42 in the larval 
stage, and 109 in the egg stage. Whatever may have been the cause 
of the dying of the larvee and pupz, I am sure that at least a large 
percentage of the eggs was eaten, because many times I found eggs 
in the nest that had been partly eaten. 


13 


Assuming that the first larvee hatched from the first eggs, we have 
the following egg periods for the first 27 larve: 


For the first egg, 47 days For the next 2 eggs, 34 days 
a next (1),-47 days nthe Game): 33 days 
ee eta davis any ithe alee Ce 36 days 
et) a Cole datidays Ren suns ena 35 days 
Brin 2 (1) cagndays Rey ee Oe 33 days 
“ “ “ (1), 40 days * ‘ A (aL), 34 days 
cee ce « (1), 41 days son ag HESS ate SS Gi)F 31 days 
“ “ “« (5), 39 days < os “¢ (1), 27 days 
“ « © (1), 38 days ic Ga 736. dey 


On the same basis we find that the length of the larval stages for 
the first 15 larvee are as follows: 


For the first larva, 16 days For the next (1), 22 days 
- SeeTrextach) = 19) oc ih s a (Gill) eae ee 
“ce “ce “ce (Ge 19 “ “cc “ “é (G1)). 32 “ 
“ce “ “ (1), 20 6e “cc “ce “cc (aly) 32 “cc 
“ “ “cc Gy 21 oé “ce “ee “e @) 34 “cc 


“ “ “ . (1), 22 “ “cc “ce oe (2): 39 “ 
“ce “ce “ (OQ). 93 “cc ? 


For the next few that transformed the time was still longer, but 
could not be determined exactly since some of the larve disappeared. 
The pupal stages for the first 15 adults are as follows: 


For the first (1), 22 days For the next (1), 29 days 
$ toe MEXt (3), 23) is “ sea Ce) eon use 
“cc “ “ (2); 24 “ce “ “c “ (Gal) 37 “cc 
ae v§ (GD) Pas “ 4 aa Gl) saee os 
“ “ “ce ()s 26 “ “cc “ce “ (GD), 33 “ce 


“ “ “ec (Gib) 37 “ee 


CoLony 27a* 


Date Eggs Total |} Larve | Total Pupe | Total |} Adults} Total 


Mar. 1 1 1 
os Slewsiee 3 4 
of Sues 3 if 
vt 7 6 13 


*In this table the asterisk signifies missing; and the dagger, accidentally in- 
jured or destroyed. 


14 


COLONY 27a—Continued 


0 
rs 


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Or 


cw) 
or) 


2 0 
No} 


TOD OH 


le 2) 


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wnwnro 


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res 


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. 
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Total 


Larvee 


oor OW SO W WwW 


Total 


NTKNorwose osnDnDnanw 


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wore 


Pup 


Total 


Adults 


Total 


15 


CoLony 27a—Continued 


Date Eggs Total || Larve | Total | Pupe | Total |} Adults! Total 

May 9 1 68 1 13 1 1 

aly 5* 61 2 14 1 2 

eee: dal: ty 68 2* 12 0 2 

rake £12 5* 62 1 13 0 2 

me lS): a 62 1 14 0 2 

rok i'd! 5 64 3 17 0 2 

Ae es ier 0 61 3 19 1 3 

cium 1G 3* 58 0 19 0 3 

seu Ny 8 66 0 19 0 3 

ses) i 53 6 25 0 3 

pm Ee) ily 52 1* 24 1 2 

foe 0 4* 48 0 23 1 3 

see OTL 6* 42 0 22 1 4 

i PPI 1* ot 4 25 1 5 

Soe 23 2* 34 1 26 0 5 

shee As: 33 4 30 0 5 

EF | ee date 3* 30 4* 26 0 5 

Se O Gis <a 2 32 0 25 il 6 

Biron 35 1 25 1 7 

a): ee 1* 32 0 25 0 if 

hy Me ae 4* 28 0 25 2* 5 

at SO. 0 28 0 24 ib 6 

a ae 0 28 ib 22 il Uf 
une: +1... 0 28 0 22 0 a 

Ze POO 4 30 2 23 il 8 

4 bs 0 30 23 0 8 

ms Ne 3 3 2* 21 0 8 

. 6.. 2 35 2* 19 0 8 

- UE 8 42 1 19 1 9 

eS Sins 1 43 1* 17 1 10 

prea UG: 2% 41 3* 14 0 10 

eet 0 a 7 48 0 14 0 10 

peered 0 48 0 14 0 10 

tte Ke, ale 47 0 14 0 10 

= 3 1 47 1 15 0 10 

des aa ts 30* 17 0 14 1 « 4 4 

Secon? ae 0 } 17 3* 10 1 8 1* 3 

a0. 2 | 17 2 12 3* 5 0 3 

Mh ps Is stand Nae 1* 11 1* 4 1* 2 

<a UDO 12* 1 1* 8 2 4 2 4 

ered. 6 i 0 8 0 3 1 5 

me. 25% 1 8 0 8 1* 2 0 5) 


Total 


| ae ad HOH SH SH RR OM OD OD OD OD OD OD OD OD HID SH SH SH 29 2D 20 219 1 10 26 20 2 1 1) 19 19 1H OH OH HH H tH 


16 


CoLtony 27a—Concluded 


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oetet seiner ee erm Ste) on vaca ee ey ee See ee oe es Se cia en eae Sia eens uae ou 
~ =] v 
tan ee < n 


17 

I was obliged to neglect the colony for several days arid as a re- 
sult it perished. 

This queen laid a total of 302 eggs, from which but 11 adults were 
reared; 11 individuals disappeared in the pupal stage, 30 in the 
larval stage, and 228 in the egg stage. Not all the young that dis- 
appeared in this case were eaten by the queen, as it sometimes hap- 
pened that they were placed in the condensed moisture around the 
sponge and spoiled. 

It is not possible to get the exact length of the stages in this col- 
ony, since some of the eggs disappeared before any had hatched, some 
of the larve disappeared before any had pupated, and some of the 
pupze disappeared before any adults emerged. However, if we as- 
sume that the first 6 eggs passed through all the stages and became 
adults, the stages would be as follows: 


For the first egg, 48 days For the next egg, 47 days 
For the next 2 eggs, 46 days For the next 2 eggs, 44 days 
For the first larva, 21 days For the first pupa, 40 davs 

“ “ next “cc 99 “ “ “ce next “ 39 “ 

“ “ee “ “c 27 “ “ “ “c “cc 34 “se 

“ “ce “ “ 31 “ce “ “cc “ ec 29 “c 

o “ “ “ 32 “ce “ “cc “cc “ 33 “ec 

“ee “ “ “c 33 ity “ “ “ “cc 32 it3 

COLONY 30 


This queen was taken as a solitary female from her cell in a corn 
field by G. E. Sanders on May 7. At first Ihad her in the same nest 
with another queen taken the same day. On May 18, 3 eggs appeared 
in the nest, and on May 19, 2 more. I then removed one queen and 
the 5 eggs. The remaining queen laid no eggs until May 206. 


CoLtony 30* 
Date Eggs Total | Larve | Total | Pupe | Total | Adults) Total 
OE iad Se 
coat EP ie Sa pt uf 
aM IG a taree 1 8 
Rae Oe. a 1 9 
es0o, 5 14 
OE 2 16 


*In this table as heretofore, the asterisk signifies missing; the dagger, injured 
or destroyed. 


18 


Cotony 30—Continued 


Date Eggs Total 
June 1 0 16 
este 2 18§ 
* Dae 3 18 
2 (55 1 17 
- ioe 0 ile 
ay San 4 21 
SiO 0 21 
ae 6 27 
18} 8 35 
Sees 7 42 
SEO 1 42 
Senior (ley resi 5 44 
he atolls 2 43 
Oa we 0 42 
he een ree 2 41 
O25 6 44 
: 26 4% 40 
Sra leo ae ee 2 42 
29 40 
3 is 37 
July 2 3* 30 
SS 4 4* 24 
i Seo 0 21 
me Gare 3* 17 
Ape ats 4 21 
a Oia 3 23 
See OK a 0 33 
ae Salil 3* 20 
os Flats 4 24 
oY ale 0 24 
Sule 11 34 
Pe lbiae 0 34 
2 ABs 0 34 
area Ly 2 3 
i oe cealhe) 0 34 
Sh aL OE 0 32 
rb aD (Rae Oe a 30 
Ad See ailieyre 4° 26 
See OD ae 0 26 
Ste OBE oad 0) 26 


$I destroyed 3, leaving 15. 


Larve 


Hr 


Wr OW We WH ee 


2 


RB ww Pp 


%* 


WOO eS SO (Oh OE, 0 


SS wae vw) © 


Total 


a 
~t Or 


wo WwW WwW 
ao ao 


Pupe 


wooowdcrecreod9ocrrFCoco$d oO CF 


Total 


Awwwwnnn wore eYeHy eH 


Adults 


Total 


19 


Cotony 30—Concluded 


Date Eggs Total || Larve| Total Pupz | Total |} Adults| Total 

od: Ifa 25 1 23 1 vg 
Seen 55 0 25 0 23 0 q 
Smee Ole 0 24 1 24 0 7 
kb aa 9 32 1 24 il 8 

Aug. 1.. 0 32 0 24 0 7 1 t 
. BIS e 8* 24 Q* 22 0 1 0 1 
s AS. 0 24 0 22 1* 5 1 2 
“ Tears 0 24 0 22 0 5 0 2 
as 0 24 0 21 1 6 0 2 
aS lige 0 24 0 20 1 6 1 3 
“ 9... 0 24 0 19 1 iG 0 3 
er ar (0) 4* 20 2* il7é 1* 5 1 4 
te Silat 0 20 0 NG, 0 3 2 6 
Soe 0) 20 0 17 0 2 1 y 
Be Sale! 0 20 0 16 1 3 0 us 
eel G 0 20 0 15 1 4 0 7 
oly iy 3* ih7¢ 3% 12 0 3 1 8 
oe ake 2* 15 0 11 1 4 ale t¢ 
pom Oe. 0 15 0 11 0 4 0 t 
20 0 15 0 10 iteclee ks 0 7 
pe BROS < vi 22 1% 9 0 5 0 tf 
ey, Bina esd 1* 8 0 5 0 7 
rm, (30 6 28 2* 5 1 6 0 7 

Sept. 3 0 28 0 5 0 6 0 i 
12>) eee 14* 14 3* 2 3* 1 2 9 
Be OB Is oe 5 4* 10 0 2 0 1 0 9 

Oct. SIS Ae 0 8 2 4 0 1 0 9 
os 1 OE 0 8 0 4 0 0 il 10 


There was no further development of this colony, as the weather 
became too cool. Several adults died. December 2, I transferred 
the colony to a warm room. December 20 the queen began laying 
again, and by January 10 she had laid 17 eggs. January 19 the queen 
died and the colony was discarded. 

Assuming that the first 6 eggs developed into the first 6 adults, 
the lengths of the various stages are as follows: 

For first egg, 24 days; for next 3 eggs, 25 days; and for next 
2, 26 days. 

For first larva, 22 days; for next one, 25 days; for next one, 
28 days; for next one, 33 days; and for next (2 larve), 32 days. 

For first pupa, 21 days; for next (2 pupe), 20 days; for next 
pupa, 18 days; and for next (2 pup), 19 days. 


20 


This gives for the first 6 eggs an average time of 25 days; for 
the first 6 larve, 28.6 days; for the first 6 pupe, 19.5 days. 

In colony 27) the average time for the first 6 eggs is 44.5 days; 
for the first 6 larve, 19.5 days; and for the first 6 pupae, 23 days. 
In colony 27a the average time for the first 6 eggs is 46 days; for 
the first 6 larve, 28 days; and for the first 6 pupz, 34.5 days. 

The queen in colony 30, laid a total of 110 eggs, from which 11 
adults were reared. Five individuals disappeared in the pupal stage, 
18 in the larval stage, and 64 in the egg stage. 


COLONY 28 


April 5, I took a solitary queen from her cell in a corn field and 
placed her in a Fielde nest under normal temperature conditions. 
She began to lay May 16. By August 25, when she died, she had 
laid 54 eggs, from which but one adult was reared. ‘Twenty-four 
individuals disappeared in the egg stage, 27 in the larval stage, and 
one in the pupal stage. Forty-eight of the 54 eggs were laid between 
May 16 and June 2. After that date the queen did not seem to do 
well. The lengths of the egg periods for the first 6 eggs are as 
follows: for the first (1), 25 days; for the next (1), 24 days; and 
for the next (4), 25 days: 

Because of the fact that this queen did not take good care of the 
young, most of them perished and | could not get the lengths of 
the stages. 


COLONY 18 


This queen was carried over winter in a Fielde nest in a warm 
greenhouse. She began laying April 10. By June 27, when she 
died, she had laid 93 eggs. But 3 pupze were reared from these, 2 
disappeared in the larval stage, and 61 in the egg stage. The lengths 
of the egg stages for the first 6 eggs are as follows: for the first 2 
eggs, 26 days; ior the next A,eees,. 23 Gays. 

This gives an average of 24 days as the length of the egg period 
for the first 6 eggs. No eggs disappeared in this nest until after the 
larvee appeared, so the stages here may be taken as exact. 


COLONY I8c 


This queen was taken in the fall and carried over winter in a 
warm greenhouse, but on March 25, before she had laid any eggs, 
was transferred to a room where the temperature was normal. She 


21 


began laying April 27, and by June 10, when she died, had laid 45 
eggs; but they kept disappearing from time to time, and none of 
them hatched. 


COLONY 18d 


This queen was taken at the same time as the one in colony 18c, 
and kept under the same conditions. She began laying the same day, 
April 27, and by July 31, when she died, she had laid 114 eggs, but 

for the same reason as above, none of them hatched. 


COLONY 26a 


This queen was kept over winter in a warm greenhouse. She 
began laying February 27, and by September 3 had laid 140 eggs, 
from which but two adults were reared. As so many disappeared 
at different times I could not get the lengths of the various stages. 


A large number of the queens which I used for starting colonies 
lived only a few weeks or months and did not bring any young to 
maturity, although all laid eggs. Some of them seemed to eat a 
large percentage of the eggs, while others simply allowed the eggs 
to spoil. Three other queens may be mentioned. The one in Colony 
B, No. 1c, taken in April and kept under natural conditions, produced 
2 workers and 11 larve by September 15. The egg period for the 
first 2 eggs was 24 days. The egg stages for the first 3 larve were 
21, 24, and 25 days, respectively. The pupal period for the first 
adult which emerged was 26 days. 

In Colony B, No. 1d, the queen produced g workers by Septem- 
ber 7. 

Colony B, No. 1/ was kept under practically normal conditions. 
The queen was taken about the middle of April and kept with some 
others until June 24, when I placed her in a Barth nest, made by 
placing a glass cylinder 3 inches high and 3 inches in diameter inside 
a cylindrical glass jar 4 inches high and 4 inches in diameter, and 
filling the space between the cylinder and the jar with moist sand. 
The top was then covered with a layer of cotton batting, and this 
was held down by a pane of glass. The queen began to burrow at 
once, and by June 30 had made a complete cell at the bottom of the 
sand and had deposited several eggs. In forming her cell the queen 
had completely closed the burrow by means of which she reached 
the bottom of the sand. With such a nest it was impossible to take 


22 


daily observations as to the number of young, but I have the follow- 
ing notes on the development of the colony :— 

August 3, I count 15 cocoons and see a number of eggs and 
larve; Aug. 8, I count 21 cocoons; Aug. 17, three callows have 
emerged; Aug. 20, there are 5 callows today. 

August 25. There are at least 10 callow workers today. They 
are very active and have excavated a tunnel nearly 6 inches in length 
around the bottom of the glass jar. They have moved some of the 
brood about 1% inches from the original cell of the queen. 

August 28. There are 15 callow workers. Very active. Their 
main tunnel is about 10 inches in length and is started upward. It 
is half-way to the top of the cylinder. 

August 29. They have excavated to the top of the sand. 

I did not break up this nest in order to get the exact count, but 
the approximate count at the end of the season was 15 to 17 workers 
and 1 larva. No pupe or eggs. 

The seven cases in which the queen succeeded in founding a 
colony and living through the season are as follows. 


Number of colony | Number of workers produced Total number of eggs 

27b ial 222 
27a 27 302 
30 11 110 
26a 2 140 

IB, INGO, ike 2 

B, No. 1d 9 

Bey NiOne tl 16 


This gives an average of 11 workers produced by a queen in one 
season, with a maximum of 27. The average number of eggs laid 
by the queens in the four cases in which I was able to get the en- 
tire count, is 193.5. The first-year workers are very small, on account 
of insufficient nourishment. 

The above data show that sexual forms are not produced the 
first year. It is not at all likely that they are produced the second 
year because of the very greatly increased amount of nourishment 
required for producing them. After the second year the average and 
maximum colonies probably increase very rapidly, as the number of 
workers is then large enough to provide plenty of nourishment for 
the queen to lay a much larger number of eggs. 


23 


The following data show how much more prolific the queen is 
when she is well nourished by a large colony :— 

July 7, I took the old queen from a large colony of L. niger 
americanus under a stone and brought her to the laboratory. At 
10:00 a. m. I placed her in a vial by herself. By 4:00 p. m. she had 
laid 125 eggs, an average of 31 an hour, or one every two minutes. 
I removed her from the vial and placed her in a Petri dish with five 
workers from the same colony. 

July 9, 9:00 A. M. Moisture from the sponge had collected in 
the bottom of the Petri dish, and the queen and workers were nearly 
drowned. ‘The queen, however, had laid 168 eggs. I placed her in 
a dry vial. She began laying again at 11:45 and by 2:00 p. m. had 
laid 48 more eggs. Thus in a little more than two days this queen 
laid 341 eggs, or more than the average of the total number laid 
by the four first-year queens in an entire season. 

August 13, | took the old queen from a very large colony of L. 
niger americanus, brought her to the laboratory, and placed her in a 
Petri dish at 5:30. I watched her continuously for 30 minutes, dur- 
ing which time she laid eggs, at fairly regular intervals, at the rate 
of about one every two minutes. By 6:00 p. m. she had laid 16 
eggs. By 11 o'clock the following morning she had laid 166 eggs, 
an average of 9.5 eggs an hour. Between 11:00 A. M. and 12:00 M. 
she laid 6 more eggs. 

By the beginning of the third year the average colony is so large 
that, if suitably located, it can furnish sufficient nourishment to 
cause the queen to produce a much larger number of eggs and also 
to feed the increased number of larve. Such a colony might be 
sufficiently large for the workers to feed a certain number of the 
larve heavily enough to produce, not workers, but winged females. 
Some colonies, however, as those that produced but two workers the 
first year, might be no larger at the end of the second or even at the 
end of the third year than the more fortunate ones at the end of 
the first year. Such colonies would probably not produce females 
until the fourth or fifth year or even later, on the assumption that 
the difference in the production of workers and females is a differ- 
ence in nutrition, which I believe to be the case. If a colony con- 
taining brood but no queen is supplied with an abundance of food, 
they will segregate a number of the larve, feed them more heavily 
than the others, and cause them to produce queen larve. 


24 


HIBERNATION 


With the approach of cold weather the ants become inactive and 
gather together in a few of the main galleries of the nest with their 
larve, occupying at that time a very limited region compared with 
the large area occupied by their extensive tunnels in the summer 
time. I have never found anything but queen, workers, and larve 
in the nests in late fall, winter, or early spring. I have never found 
males or winged females of this species in winter, although it is quite 
common to find the winged forms of some other species in the nests 
during the winter. This shows that the winged forms all leave the 
nests in the summer or autumn. My observations show that the ants 
are very little, if any, deeper in the soil in winter than in summer. 
In fact, they seem to use their largest summer tunnels for their 
winter quarters. The first few days of January, 1909, were very 
warm. ‘The frost was out of the ground in the open fields so the 
farmers could plow. January 4, I followed a plow in an old corn- 
field, and found in the bottom of the furrows a large number of nests 
of L. niger americanus exposed, just as one finds them in the spring 
and summer. ‘The ground was so cold that the ants were quite stupid 
and very inactive, and they were huddled together in masses with 
their larve. Such masses could be picked up in places by handfuls, 
when the ants would very slowly crawl about over one another. They 
were far too stiff and inactive, however, to have moved with their 
large bunches of larve from the deeper galleries during those few 
warm days, so they must have been in these same galleries during 
the previous part of the winter, and would have remained there all 
the rest of the cold weather. As the ants were warmed by the heat 
of the hand, or that of the laboratory, they soon became as lively as 
ever and resumed their normal activities. 

Drouth will drive the ants down into the soil much deeper than 
cold. In very dry weather I have followed their tunnels to a depth 
of 22 inches, and often in the summer time many of their main 
galleries are eight to ten inches deep. In the fall of 1909 I marked 
a number of nests of L. niger americanus in an old corn-field, and at 
various times during the following winter examined one or more of 
them. I found the ants at the depths one finds them during the sum- 
mer, that is, from just below the surface to eight and ten inches 
down. Most of the ants and their larvee were from four and a half 
to seven inches down, aithough I found some not more than two 
inches below the surface when the ground was frozen to a depth of 
five and six inches. When the ground was frozen the walls of the 


25 


cells were covered with a thin layer of ice, inclosing the ants and 
their larve in an icy cell. These ants on being thawed out became 
active immediately. In two of these nests I found eggs of the corn- 
root louse, Aphis maidiradicis Forbes. ‘These were in little packets 
in cells by themselves, not with the larve. In the nest containing 
the largest number of eggs, the cells containing the eggs of the plant- 
louse were four and a half inches below the surface. By working 
carefully with a trowel I was able to get the largest packet of eggs 
out with very little dirt, and on taking them to the laboratory and 
counting them I found that I had thus separated 894 eggs, and as 
‘there were other smaller packets in the nest, there was probably 
twice that number of aphid eggs in the nest altogether. These eggs 
had probably been laid by oviparous females which had been carried 
down into the galleries by the ants. November 10, I found one 
oviparous female and some eggs in the galleries of a large colony 
about 5 inches below the surface, although the main galleries of this 
nest extended downward to a depth of from 12 to 18 inches. In 
such nests the youngest larvee were in the deepest portions of the 
nest, while the larger ones were nearer the surface. 

The fact that larve are found in the nests during the winter 
shows that the length of the larval period is variable, depending upon 
temperature, and also probably upon other factors, as nourishment, 
moisture, etc. If a colony containing a large number of larve all of 
about the same size be fed heavily, the workers do not feed the larve 
uniformly, but separate a relatively small number from the rest and 
give them much more nourishment, which causes them to pupate 
much sooner. Then they separate a few more and feed them in the 
same way. The latter may have hatched as early as the former, but 
their larval period is much longer. 

In one of my colonies some of the larvee remained as such for 
more than a year. ‘This colony was collected November 6, and con- 
tained about 300 workers and a large number of larvee but no queen. 
I kept them for a while in the greenhouse mentioned above, but 
about the middle of the winter transferred them to a warm room 
and fed them heavily. The larve began to grow rapidly and on 
March 2, 25 of them spun cocoons. The next day there were be- 
tween 75 and 100 cocoons in the nest, and new cocoons were formed 
every day from that time. It was interesting to see how busy the 
ants were when so many larve were spinning cocoons at once. Every 
larva, when it was ready to spin a cocoon, was covered with fine 
pieces torn from the sponge, or other debris, in order to give it 
something to which to attach its first silken threads. As though to 


26 


avoid a useless expenditure of labor, these larve were not scattered 
about indiscriminately, but were mostly placed in one heap consist- 
ing of seven or eight layers reaching from the floor to the ceiling of 
the nest, so that the same pieces of debris would serve for more than 
one larva. One evening I placed a piece of boiled lean beef, about 
I cm. square and half as thick, in the nest for food. By the next 
morning it had been torn into shreds, and these had been used by 
the ants in covering the larve. If the larve failed to attach their 
threads the result was naked pupz. I saw one larva that had acci- 
dentally wriggled out of its half-spun cocoon; later it became a naked 
pupa. When a cocoon was finished the workers removed it from 
the pile, carefully cleaned off the bits of sponge, meat, etc., and 
placed it with others in a clean pile. When the adult is ready 
to emerge the workers remove the cocoon from the pile, bite it open, 
and help out the young callow. The workers had placed thirty of 
the larve in one pile, and had fed them so heavily that they were 
forming queen larve. By March 10 these were about twice the size 
of the full-grown worker larve. March 15, this nest showed the 
most distinct grouping of the inhabitants of the nest I have ever 
seen. ‘There were seven distinct groups. These were (1) the thirty 
queen larve, (2) the buried larve spinning cocoons, (3) a small 
bunch of cocoons with the naked pupz (there were 15 naked pupe), 
(4) all the rest of the cocoons (more than 100), (5) the nearly 
full-grown larve which were feeding heavily (these had their an- 
terior ends pressed against a bit of egg, and with a lens one could 
see their jaws working as they ate their food), (6) the youngest 
larve, but little larger than the egg, and (7) those larve inter- 
mediate in size between those of groups 5 and 6. On March 26 the 
first three adults emerged and the next day seven more. This gives 
a period of 24 and 25 days for these pupe. ‘The empty cocoons 
were carried over to one corner and placed in the waste heap. On 
April 1, one of the queen larve was partly eaten, and from that time 
these gradually disappeared, one or two a day, until May 5, when the 
last two were eaten with the exception of one that had spun a cocoon 
on April 19. During all this time I kept the colony well supplied 
with food consisting of sugar-water, egg yolk, boiled beef, and in- 
sect food such as white grubs, pieces of flies, beetles, etc. On May 
5 the queen pupa was taken out of its cocoon, formed on April 109. 
The following notes show something of the rate and time of deposi- 
tion of chitin :— 

May 10. ‘The queen pupa shows a deposit of chitin at the edge 


of the mandibles, making a brownish line along the teeth. All the — 


27 


rest of the surface is white excepting the compound eyes and ocelli, 
which are already dark,—the compound eyes very dark, and the 
ocelli a light brown. 

May 11. The pupa has acquired a light brown tint all over. The 
teeth of the mandibles are darker and the brown is beginning to go 
back over the rest of the mandible. 

May 12. The general color of the body is a little darker. 

May 13. Still darker. 

May 14. The queen has emerged. 

This gives a period of 25 days for the queen pupa, the same as 
_that for the first few worker pupe. ‘This female never seemed to 
be healthy, and died on June 30. 

There were no more larve produced by this colony. ‘The rest 
of the larve continued to pupate and adults continued to emerge 
until July 7. On that date there were no more cocoons in the nest, 
and none of the larve which were in the nest over winter. All the 
adults which emerged were workers except the one female. There 
were no males. 

April 4, I noticed for the first time a bunch of 40 or 50 eggs. 
These were of course worker eggs, as there was no queen in the 
nest. By May 1 there were several hundred eggs. May 11 I esti- 
mated the number to be at least 500, and quite a number of them 
had already hatched. By July 7 all the eggs had hatched, so there 
were in the nest at that time only the workers and 500 or more 
larvee, all being the offspring of worker eggs. No more eggs were 
laid and none of the larve pupated during the rest of the summer nor 
the following winter, although I kept them all the time in a warm 
room and gave them plenty of food. The first cocoons were spun 
on July 4, 1910, when 8 of them were formed. The exact length 
of the larval period could not be determined, but it must have been 
more than a year, since a considerable number of the eggs had 
hatched by July 7, 1909. July 18, 1910, there were 30 cocoons in 
the nest and a small bunch of worker eggs were laid. It had been 
over a year since any eggs had been laid in the nest. More eggs 
were laid later on—about 50 or 60 altogether; not nearly so many 
as the year before. However, a large number of the workers had 
died during the year and many of the larve had been eaten, so that 
the colony was not nearly so large as the year before. July 24 the 
first adult emerged; a second, July 25; a third, July 26; and a fourth, 
July 27. These were all males. This gives a pupal period of 20, 21, 
22, and 23 days for these males. ‘This nest was examined every 
day during the summer. Cocoons continued to be formed and adults 


28 


continued to appear until the last of September, and although I 
watched carefully for the appearance of callow workers, every adult 
proved to be a male. These males did not seem to do well, as there 
were never more than 15 or 20 males in the nest at the same time; 
but there were certainly more than 100 that emerged. This agrees 
with the general opinion that the offspring of unfertilized eggs of ants, 
as well as of bees, are always male, although Mrs. Comstock 
(Wheeler, ’03) obtained normal workers from worker eggs. In a 
small queenless colony of Formica schaufussi that I watched, the 
offspring from worker eggs were all males. This brings up the 
interesting question as to whether the fertilized eggs of a fecundated 
queen ever produce males. Certainly they do not the first year, and 
most probably not the second. It is worthy of note that the same 
conditions which will develop winged females in a colony, that is, 
optimum conditions of food, temperature, and moisture, will also 
cause the workers to lay eggs and thus bring about the production of 
both the sexual forms. 

The probable life of a colony is but a year or two years longer 
than that of the queen which founded it. After the queen dies the 
eggs laid in the nest will all be worker eggs and produce males. In 
strong colonies a few eggs would also be laid the second year, but the 
next year the colony would perish, or perhaps serve as a host for some 
species whose queen is temporarily parasitic upon L,. niger americanus, 
as I have shown to be the case with Lasius wmbratus var minutus 
(Tanquary, ’11). Or it may serve as the host of young dealated, 
fertilized females of the same species, just descended from their nup- 
tial flight, as I have shown that at times such queens may be adopted 
by small queenless colonies of this species (’t1). The death of the 
queen the year before must account for my finding large colonies of 
this species which contained many hundreds of males but no females. 


SUMMARY 


1. Dates for which I have evidence of nuptial flights of Lasius 
niger americanus are September 5, 9, 18, 20, 19 to 29, October 4, 11, 
and 18. 

2. The flights generally occur in the afternoon between 3 o'clock 
and 6 o'clock. 

3. The time of a flight is partly determined by weather conditions. 

4. Fertilization probably takes place in the nest. 

5. The young queens eat a large proportion of their eggs. 


29 


6. The length of the different stages varies with conditions. The 
larval stage may extend over more than a year. 

7. The average number of adults produced in a season was eleven, 
and the maximum number, twenty-seven. 

8. The number of eggs laid by a queen depends upon the amount 
of nourishment she receives. In large colonies she may lay at the 
rate of more than one hundred eggs per day. 

g. During the winter, nests of this species contain only dealated 
females, workers, and larve. 

10. The winter quarters of this species are at about the same depth 
as those of the summer. 

Ants taken from winter quarters in a frozen condition re- 
sume their normial activities at once upon being thawed out. 

A single colony of L. niger americanus may carry through 
the winter more than one thousand eggs of Aphis maidiradicis. 

13. A small percentage of the pupz of this ant are naked, some 
of them owing to a failure of the larve to attach their first silken 
threads. Naked pupz occur among those of a first-year colony as 
well as in older colonies. 

14. The workers seem to be able to produce queen larve by fur- 
nishing plenty of food. 

15. The workers will eat some of the larve, even though plenty 
of food is provided. 

16. If a colony of workers is heavily fed it will produce a large 
number of eggs. 

17. The adults from such eggs in all my colonies were males. 

18. A colony probably does not continue to exist longer than the 
second year after the death of the queen. Such a colony may adopt a 
young fertilized female of the same species just descended from the 
nuptial flight, or may serve as host for the queen of another species 
that is temporarily parasitic upon Lastus niger americanus. 

19. Colonies of Lasius niger americanus are founded in one of 
two ways; (1) by the typical method or (2) by the adoption of re- 
cently fertilized females by a small queenless colony. 


ADDITIONAL, NOTES 


In one of my Fielde nests I noticed one day a larva with its an- 
terior end lying against one of the eggs, which it seemed to be eating 
in the same way as described earlier for the small bits of egg yolk. 
On examining with a lens I could see that about one half of the egg 


30 


was already eaten and that the larva was still feeding. This may be 
one reason why the workers keep the eggs and the larve separate. 

The sense of taste seems to be well developed in ants. They 
quickly discriminate between honey and sugar water and much prefer 
the latter to the former. On one occasion, instead of using sugar 
water, as usual, I placed a drop of honey in each nest. Generally the 
drop of food was discovered almost immediately and within a few 
minutes surrounded by the eager workers. On this occasion I ex- 
amined the nests a few minutes after the introduction of the food, 
and in only seven out of the 26 colonies were there any ants at the 
honey, and only a few in those cases. On another occasion I intro- 
duced a drop of honey and sugar water at the same time in the light 
chamber of the Fielde nest containing a large colony. ‘The honey 
was placed nearer the opening into the dark chamber where the ants 
stayed, while the sugar water was placed farther beyond it and near 
the refuse heap. The water was quickly surrounded, while only a 
few ants stopped at the honey, although they had to go around the 
honey to get to the sugar water. After a few minutes some of the 
ants began, as is their custom, to carry the dead ants, empty pupa- 
cases, etc., from the refuse heap and place in the liquid food, but in 
this case it was very striking to see the way in which the ants carried 
bits of debris around the sugar water in order to deposit them in the 
honey, while the feeding ants were passing around the honey to get 
to the sugar water. After a few minutes there were 13 dead ants 
placed in the honey and only 1 in the sugar water. This shows clearly 
that the purpose of such behavior on the part of the ants is to cover 
up objectionable substances and not to enable them the better to get 
at the food. 

The queens do not often eat from the food chamber as the workers 
do, but I have seen them drinking sugar water a number of times. 
They will also cover the sugar water with bits of debris, and in some 
cases the queens stuck to the cover pane small pieces which they had 
torn from some black blotting-paper I had in the nest, as though to 
help shut out the light. They will also bury their larve when the 
latter are ready to spin their cocoons and will clean the cocoons after 
they are finished. 

The ants often use bits of sponge and other debris to block up the 
passageway between the two chambers of a Fielde nest as though to 
shut out the light from the other chamber. In the same way I have 
had colonies of A phenogaster fulva block up a passageway to shut 
out queens of A. tennesseensis which I was using for temporary para- 
sitism experiments. Is this intelligence? 


dl 


Although most of the winged forms of this species leave the nests 
in summer or early autumn, I have a note from Messrs. W. P. Flint 
and G. E. Sanders, reporting the finding of winged females in a nest 
at Galesburg, IIl., October 29, 1909. 


II. EXPERIMENTS ON THE TRAIL, FORMATION AND ORIENTATION OF 
THE ComMon House Ant, Monomorium pharaonis L, 


The little creatures that form the subject of these experiments 
forced themselves upon my attention by interfering seriously with my 
regular work and making themselves a general nuisance in the lab- 
oratory. They had a nest in some inaccessible place in the walls of 
the building, from which they formed regular trails to any substance 
in the laboratory, such as insect specimens, fruit, meat, sugar, etc., 
which they found suitable for food. A piece of fruit left lying on 
a desk in the laboratory was sure to be found by some wandering 
worker, and in an hour or so a regular trail would be formed leading 
to it, along which hundreds of the little workers would pass to and 
fro in the course of a few minutes. 

For my regular experiments I was keeping in Fielde nests a num- 
ber of colonies of the common corn-field ant, Lasius niger americanus, 
which I often fed with sugar dissolved in water. The little /. phara- 
oms could crawl in under the roof-panes of these nests to the food 
provided for the Lasius colonies and many times caused the death 
of an entire colony in a single night. I do not know just how the 
L. americanus ants were killed. I never saw a M. pharaonis attack a 
living worker of the former species, but in some way its presence in 
the nests in such large numbers so irritated the corn-field ants as to 
cause their death. [ have seen workers of M. pharaonis attack a queen 
of L. americanus that was already weakened to such an extent that 
_she was unable to right herself when lying on her back. 

The regularity of the trails, the closeness with which they were 
followed, and the extreme sensitiveness of the ants to slight breaks 
in their trail, made by rubbing the finger across it or placing some 
odoriferous substance or even a small piece of clean paper upon it, 
interested me, and induced me to perform some experiments to deter- 
mine whether they depended entirely upon a chemical sense, located in 
the antennz, to find their way, or whether they possessed also a sense 
of direction. While I was working on this problem other questions of 
-a similar nature presented themselves which I tried to answer by ex- 
periments, some of which are given below. 


32 


After a number of preliminary experiments of one kind or another 
I used the following simple device to serve my purpose. I took an 
ordinary spindle-file with a base 2% inches square, from the center of 
which extended upward, 7 inches in height, a cylindrical rod % inch 
in diameter. On the sharp point of this rod I stuck a circular piece 
of cork, 1 inch in diameter, which served as a support for a bottle 
containing sugar dissolved in water. Before placing the bottle of 
sugar-water on the cork I would cause the ants to form a trail to the 
bottle sitting on my desk; then I would replace the bottle with the 
file having the bottle on top, usually with 50 to roo ants feeding 
from it. So many of these ants in wandering back from the bottle 
of sugar-water would meet the ants at the base of the file, that soon 
the trail would be continued up the rod to the bottle. 


EXPERIMENT NO. I 


After a distinct trail was formed, I removed the cork with the 
bottle just long enough to thrust the rod through the center of two 
pieces of clean white note-paper, 234 inches square, one of which I 
placed one third, the other two thirds, the distance up the rod, so 
that the whole apparatus now had the appearance shown in the figure. 

In order to get down, the ants now had to go out to 
the edge of the papers on the upper side and return to 
the rod on the under side. It was several hours be- 
fore they formed a distinct trail, since they wandered 
about in confusion on the upper side of the papers and 
did not like to go over the sharp edges. When the 
trail was formed it led down the side of the bottle 
nearest the nest, down the rod on the same side, then 
in a straight line out to the middle of the edge of the 
yaper towards the nest, back to the rod on the under 
side in the same line and over the lower paper in the 
same way, so that the trail on it was exactly beneath 
the one on the upper paper, then on down the rod and 
back to the nest. 

After a good trail was formed I turned the top paper a few de- 
grees to the right when no ants were on it. The next ants that 
reached the paper, both from above and from below, instead of fol- 
lowing in the same direction followed the old trail, which extended 
at an angle of a few degrees from its former direction. I then turned 
the lower paper a few degrees to the left with the same result, that 
is, the ants followed the trail. I continued turning the top paper to- 


Bis) 


the right and the lower to the left until there was a difference of 
180 degrees in the direction of the trails on the two papers. The 
ants still followed the trail. I continued turning the papers until 
both trails again led the same way but exactly opposite to their first 
direction, with the same result. Then I tried turning the papers 
through an angle of go degrees and even 180 degrees at one turn, 
but always with the same result. The first ants that reached the 
paper after turning it through so large an angle, were a little con- 
fused by the slight break in the trail, and sometimes a few of them 
would get lost and wander about for a while, until, striking the 
trail, they would start off in a straight line. 

The above experiment I repeated a great many times and always 
with the same result; the ants followed the trail absolutely without 
regard to change of direction. This shows that, at least after the 
trail is formed, the ants, if they do possess a sense of direction, are 
not guided by it in finding their way back to the nest, but slavishly 
adhere to their trails, although the fact that the trails were formed 
on the side of the bottle and towards the edges of the paper nearest 
the nest indicates that in forming their trails a sense of direction 
may play some part. Later on I repeated the experiment, using cir- 
cular cardboard disks, 4 inches in diameter, instead of square pieces 
of paper, and found that the trails were formed in the same way, 
although quite often there was a difference of a few degrees in the 
direction of the trails on the two disks, and in some places they 
even extended in opposite directions. Usually, however, they ex- 
tended in nearly the same direction. 


EXPERIMENT NO. 2 


To determine whether the direction from which the light comes 
influences the ants in finding their way. 

In some of the foregoing tests the apparatus was sitting near a 
window, so that when the disks were turned through an angle of 
180 degrees the relation of the light to the trail was exactly reversed. 
This, however, made absolutely no difference in the behavior of the 
ants. 

In order to make another test, one evening, at 7:30, I placed an 
incandescent light 2 feet from one side of the apparatus. At 8:45 
p. m. I changed it to about the same distance from the opposite side. 
So far as I could judge from their behavior, the ants did not even 
notice the change. I repeated this experiment many times, and al- 
ways with the same result. 


Be 


EXPERIMENT NO. 3 


Can ants of this species recognize a trail laid down by other in- 
dividuals belonging to the same or to another colony? 


It would seem in the highest degree improbable that each one of 
these hundreds of ants following the trail did so only after it had 
found the food independently or had followed other ants and laid 
down its own trail, but Miss Fielde in “Further Study of an Ant’ 
(1901) makes the statement concerning another species, 4 phenogaster 
fulva picea, that each ant lays down its individual trail, which can 
not be recognized by other ants of the same colony. In order to 
test this point with M7. pharaonis I brought seven ants from another 
room of the building and placed them, one at a time, on one of the 
cardboard disks. In every instance the ant wandered about until it 
struck the trail, which it then followed, sometimes to the nest and 
sometimes to the food. ‘To be sure, the ant did not in every instance, 
especially when excited, recognize the trail the first time it struck 
it, but almost without exception the trail was recognized sooner or 
later and followed. It is very improbable that these ants had been 
on the trail before; but to make the test more sure I isolated a num- 
ber of them for several days, during which I caused trails to be 
formed on new disks. Placing these ants on the disks I found that 
they followed the trail just as the others had done. In each instance 
I was careful to place the ants to be tested on the disks at a time 
when there were no other ants there. These experiments were also 
to serve another purpose and will be referred to again. 

To find out whether ants from one colony could recognize a trail 
laid down by ants of a different colony, I had a friend whose pantry 
was infested by this same species, and whose house was at least a 
quarter of a mile from the insectary, bring me a number of them in 
a bottle. I found that they recognized the trail just the same and 
started to follow it, but that they were invariably attacked and killed 
when they met the other ants. 


EXPERIMENT NO. 4 


To determine the length of time a trail can be recognized after it 
has ceased to be used. 

January 25.—3:05 P.M. I remove the top disk, B, having pre- 
viously marked the position of the trail by placing a small ink spot 
on either side of it. . 

4:15 P.M. I replace disk B in such a way that the trail leads out 
in the opposite direction from what it did before, and in the opposite 


35 


direction to that on the lower disk. With almost no confusion the 
ants, both coming and going, led out over the old trail. The disk 
has been removed 1 hour and to minutes. 

January 26.—8:17 A.M. I remove disk B again. 

11:17 A.M. I replace disk B so that the direction of the trail 
extends at an angle of go degrees from the one on the lower disk. 
Without hesitation the ants start out from the stem over the old trail, 
but the first three from each direction go only two thirds of the 
way to the circumference and then turn back. The fourth ant from 
above goes over the edge, hesitating a little, and meets the ant on 
the under side. After that the ants go on as before. The disk has 
been removed 3 hours. 

11:20 A.M. I remove the lower disk, A. 

5:30 P.M. I so replace disk A that the trail on it extends in the 
opposite direction from that on the other disk. The first ants that 
reach the disk appear lost and wander about, but still seem to recog- 
nize the trail faintly when they cross it. In about a minute, one ant 
on the upper side of the disk follows the trail to the edge and goes 
to the under side, where it follows the trail on to the nest. Not all 
the ants seem to be able to recognize the trail, and many wander 
about over both surfaces of the disk, sometimes following it for a 
short distance and then leaving it. 

5:55 P.M. Eleven ants wandering on the upper surface and nine 
on the lower surface. Every once in a while an ant goes from one 
surface to the other on the trail. 

5:58 P.M. Sixteen ants wandering on the upper surface. 

January 27.—8:00 A.M. The trail which the ants are using this 
morning does not coincide exactly with the old trail. It goes over 
the edge of the disk at the same point, but at an intermediate point 
between the circumference and the stem it is about ™% inch to the 
side of the old trail. The disk has been removed 6 hours and 10 
minutes. 

January 26.—6:00 P.M. I remove disk B. 

January 27.—8:05 A.M. I replace disk B. The ants can still fol- 
low the trail, but it is evidently very indistinct to them. ‘The first 
ants from either direction start out over the trail, very slowly how- 
ever. They move a little way, stop, go on, turn around and go back 
to the stem and then wander about over the disk, apparently search- 
ing for a more distinct trail. Nearly all those that go over the edge 
of the disk, however, do so at the point where the old trail goes over. 
The ants follow the trail quite closely on the under side, although 
they move very slowly. I think the ants feel less like wandering 


36 


about on the lower surface because of their inverted position, and 
they therefore “smell” their way much more carefully. 

8:45 A.M. The ants are still wandering about on the upper sur- 
face of the disk. A number of them cross and recross the trail many 
times without seeming to notice it. On the lower side they are fol-’ 
lowing the trail closely. 

9:30 A.M. The ants are not yet following the trail on the upper 
side. 

10:10 A.M. The ants still wandering on the upper side, but oc- 
casionally one follows the trail. ‘Trail closely followed on the lower 
side. 

11:05 A.M. More ants are following the trail, but they still 
wander about considerably on the upper surface. 

11:55 A.M. The ants are now following the trail on both sur- 
faces. 

February 2.—4:00 P.M. The last few days I have been using 
new disks, C and D. I remove the top disk, D, and replace it with 
a fresh one, E. 

February 3.—8:00 A.M. I remove disk C and replace disk D. 
D has been removed 16 hours. The ants can still distinguish the trail 
and some of them follow it, sometimes turning and retracing their 
steps, sometimes wandering out to the side and then back, a few of 
them, however, following it with very little or no hesitation. 

9:30 A.M. The ants are following the trail as though’ nothing 
had happened. 

3:00 P.M. I remove disk E. 

February 4.—8:00 A.M. I replace disk C. It has been removed 
24 hours. The ants begin to follow the trail with about the same read- 
iness that they did the one yesterday that was removed for 16 hours. 
There seems to be even less confusion, but this is probably due to 
the fact that not nearly so many ants are passing this morning. 

220 Pan) Il remove disk: 1): 

5:30 P.M. I replace disk FE. It has been removed 26% hours. I 
can not make out positively whether any of the ants recognize the 
trail or not. I had placed a piece of fresh meat on the bottle in the 
afternoon, and a much larger number of ants are passing than usual. 
A great many ants are scattered over the surface of the disk. Some 
of them seem to follow the trail for a little way and then lose it, but 
I can not be sure that they do not just happen to follow the trail 
for a short distance. More of the ants pass from one surface of the 
disk to the other at or very near where the trail goes over the edge 
than at any other place. I watch them until 6:00 p. m. but can not 
tell whether they are going to follow the trail or not. 


37 


8:00 P.M. The ants are not using the old trail. They are still 
wandering a great deal, but seem to be following a trail at an angle 
of about 15 degrees to the right of the old one and 75 degrees to the 
left of the trail on the lower disk. 

8:45 P.M. The new trail is now fairly definite. 

February 9.—2:00 P.M. I remove disk E. 

February r0.—3:15 P.M. I remove disk C and replace disk E. 
Disk E has been removed 25 hours and 15 minutes. Most of the ants 
do not recognize the trail, but a few of them seem to do so. 

3:30 P.M. A great many ants are scattered over the disk. Now 
and then an ant seems to recognize the trail and follows it for a short 
distance, five or six of them following it over both surfaces. 

4:00 P.M. Ants still wandering about on the disk, but occasionally 
one seems to follow the trail. 

4:40 P.M. The ants are now following the trail with very little 
wandering. 

February t1.—5:30 P.M. I replace disk C. It has been removed 
26 hours and 15 minutes. I can not see that the first ants that reach 
the disk recognize the trail. I watch them for 10 minutes; most of 
them do not follow the trail but wander about on both surfaces. A 
few of them, on the lower surface, seem to recognize the trail and 
several pass over the edge at or near the place where the trail passes 
over. 

February 12.—10:00 A.M. The ants are following the old trail. 

February 16.—1:45 P.M. I remove disk C. 

February 17.—5:00 P.M. I replace disk C. It has been re- 
moved 27 hours and 15 minutes. The first ants that reach the disk do 
not seem to recognize any trail. Some start back to the nest or the 
food, and some wander about on the disk. 

5:10 P.M. I notice two ants follow the trail on the lower sur- 
face, go over the edge, and then wander about on the upper surface. 
A great many ants are wandering about on the upper surface of each 
disk. 

5:20 P.M. Now and then an ant follows the trail on the lower 
surface and loses it on the upper surface. 

February 18.—8:00 A.M. The ants have formed a new trail, 
about 65 degrees to the left of the old one and about 15 degrees to 
the right of the one on the lower disk. 


The above experiments show that a trail formed over cardboard 
by M. pharaonis may be recognized after it has ceased to be used for 
26 hours and 15 minutes. No doubt factors such as the material over 


38 


which the trail is formed, atmospheric conditions, etc., would cause a 
difference in the length of time a trail could remain unused by the 
ants and still be recognized. 

An idea of the number of ants passing over the trail in these ex- 
periments may be gained from the following counts taken at various 
times. 

January 22.—Between 11:45 and 11:50, sixty-one ants passed a 
certain point on the trail, twenty-five going to the food and thirty-six 
to the nest. 

January 25.—Between 3:00 and 3:05, ninety-seven ants passed 
a certain point, sixty-two going to the food and thirty-five to the 
nest. 

January 26.—Between 9:45 and 9:50, seventy-eight ants passed 
a certain point, thirty-nine going each way. 

February 2.—Between 11:32 and 11:37, seventy-four ants passed 
a certain point, thirty-six going to the food and thirty-eight to the 
nest. 


EXPERIMENT NO. 5 


Can ants recognize which direction on the trail leads to the nest? 

Of the seven ants (Experiment 3) placed on the trail from an- 
other room of the building, three followed it to the food and the 
other four to the nest. There is here the possibility that three ants 
sought the food purposely and that four purposely followed the trail 
to the nest. 

January 28.—2:45 P.M. With a camel's hair brush I pick up 
from the edge of the jar upon which the apparatus is resting today, 
an ant, No. 1, going to the food, and place it on top of the lower disk 
near the trail. It crosses the trail without seeming to recognize it, goes 
around the disk once, crosses the trail again, goes half-way around 
the disk again, and then reaches the stem, where it takes the trail 
and goes to the food, which it reaches at 2:50. 

2:55 P.M. I take No. 2 from the top disk, going towards the 
nest, and place it on the lower disk near the trail. It recognizes the 
trail and after a little hesitation starts towards the food. When it 
reaches the stem it turns and follows the trail back to the nest. 

3:07 P.M. I take No. 3 from the edge of the jar, going to the 
food, and place it on the lower disk near the trail. It crosses the 
trail, wanders about for a short time, then strikes the trail and starts 
to follow it to the nest. It goes over the edge of the disk to the 
stem, then on past the stem and seems to be lost for a short time, 
then back to the stem and down it to the edge of the base. There it 


39 


turns and retraces its steps over the base as far as the stem, then 
turns again and continues toward the nest. 

3:32 P.M. I take No. 4 just as it reaches the top disk, coming 
from the food, and place it on the lower disk near the trail. It starts 
on the trail toward the nest, crosses to the under side of the disk, 
then turns and comes again to the upper side, wanders about for a 
while near the edge, goes to the lower side, back to the upper, then 
on the trail again to the lower side, follows the trail to the edge of 
the base, turns and goes back about half an inch, then turns again 
and continues towards the nest. 

3:50 P.M. I take No. 5 from the edge of the jar, going to the 
food, and place it on the lower disk near the trail. It crosses the 
trail three times. The fourth time it comes to the trail it follows 
it to the food, which it reaches at 3:55. 

4.07 P.M. I take No. 6 just as it reaches the top disk, coming 
from the food, and place on top of the lower disk near the trail. It 
follows the trail at once to the nest. 


It will be noticed that the three ants taken as they were coming 
from the food, Nos. 2, 4, and 6, finally followed the trail to the nest, 
and that of the three taken as they were coming from the nest, one, 
No. 3, goes back to the nest, while the other two, Nos. 1 and 5, con- 
tinue to follow the trail to the food. This is, of course, insufficient 
data to base any conclusions whatever upon, so, later on, I isolated 
two groups of ants on islands in a pan of water for several days, 
providing one group with plenty of food and keeping the other with- 
out food. I then transferred them, one at,a time, to the new trail 
which I had caused to be formed in the meantime. The results, how- 
ever, were not very satisfactory, so I shall not give them in detail. 
It was impossible for an ant to follow the trail very far without 
meeting others, and there was often a tendency for the ant placed 
upon the trail to turn about and follow others which it met, although 
sometimes it merely stroked antennz with them and went ahead. 

An experiment along this same line consisted in removing one of 
the disks and replacing it with the lower side uppermost, thus re- 
versing the direction of the trails on both surfaces. This caused 
some confusion, but I think no more than was caused by merely re- 
moving the disk and replacing it in the same position. Although the 
above experiments are not at all conclusive, yet it seemed to me that 
the ants merely recognized the trail as such, and could not tell which 
direction on the trail led to the nest. I did not find in the behavior 
of these ants any support for Bethe’s ‘‘Polarized Trail” theory. 


(Bethe, 1902.) 


40 


ADDITIONAL NOTES 


Whenever I caused a new trail to be formed, or placed on a new 
disk, I always watched carefully for any signs of communication 
when the first ants from the food met those from the nest. One would 
think that these conditions would be ideal for any power of communi- 
cation on the part of the ants to manifest itself, since the ants on 
one side knew the way back to the nest and were searching for the 
food, while those on the other side knew the way to the food and 
were trying to get back to the nest. ‘Yet I failed to observe anything 
in the behavior of the ants which I could interpret as communica- 
tion. ‘To be sure the ants meeting under the above circumstances al- 
ways stopped and stroked antenne, but when they separated each con- 
tinued to wander as aimlessly as before, and the gap in the trail was 
finally bridged by the ants from one side accidentally striking the 
trail on the other. I do not, of course, mean to say that communi- 
cation among ants does not exist. In fact, stridulation, gestures, 
postures, etc., on the part of the ants undoubtedly do represent some 
form of communication, as has been shown by Wheeler, Forel, and 
Wasmann. I do mean to say that with this particular species and 
under these particular conditions I failed to observe anything, which, 
from its effect upon the behavior of the ants, I could interpret as 
communication. 

As a rule the queens of M. pharaonis do not leave the nest to 
feed, but quite often when I placed out some food particularly at- 
tractive to the ants, such as a piece of fresh beef, especially if the 
room was quite warm, a number of queens would follow the trail out 
to it. Ordinarily, however, they did not feed, and I think they were 
only induced to come out by the fact that a very large number of 
workers was passing in and out. During the winter I captured fifteen 
dealated queens from this one colony. 

The queens follow a trail just as the workers do, and without 
having been over it before. One rather amusing illustration of this 
was exhibited when I placed a queen, previously isolated, upon a disk 
having a newly formed trail on it. I first removed the disk from the 
apparatus and held it in my hands during the experiment. The queen 
wandered about until she struck the trail, which she at once began 
to follow. She followed it over the edge to the lower surface, where 
she continued until she reached the hole in the center of the disk 
through which the rod had passed. After a little hesitation she 
crawled through the hole to the upper surface, coming out on the 
trail above, and thus making it continuous. She continued following 


41 


the trail, going over the edge to the lower surface, back through the 
hole in the center, until she had completed the round more than a 
dozen times. After that she seemed to realize that she was not get- 
ting anywhere and began to wander about. 


CONCLUSIONS 


1. A trail once formed by Monomorium pharaonts is followed 
regardless of any change made in its direction. 

2. Change in the direction from which the light comes does not 
influence this species in following its trail. 

3. Ants of this species can recognize a trail laid down by other 
individuals of the same or of a different colony. 

4. Monomorium pharaonis can still recognize a trail sufficiently 
well to follow it, after it has ceased to be used for at least 26 hours 
and 15 minutes, 

5. The behavior of ants of this species when placed upon the 
trail seems to indicate that they do not recognize which direction leads 
to the nest. 

I do not, of course, attempt to apply these conclusions to all ants, 
for a study of the literature upon ants, or, better still, a study of 
the various species of ants themselves, will soon convince one that 
there is probably as much diversity in the habits of different species 
of ants as there is in the habits of different species of mammals or 
of birds. It is probable, however, that they may apply more or less 
closely to those species of ants which have very small eyes and travel 
in regular files. 


EMBRYOLOGICAL STUDIES 


STUDIES ON THE EMBRYOLOGY OF Camponotus herculeanus 
var. ferrugineus Fabr. AND Myrmica scabrinodis 
var. sabuleti Meinert 


METHODS 


The eggs for the studies on the first species were obtained from two 
large colonies of Camponotus herculeanus var. ferrugineus which I 
kept through the winter in large Fielde nests (Fielde, 1904). ‘The 
temperature of the laboratory in which they were kept was about 70 F., 
and remained practically constant day and night. Each colony con- 
tained one queen. The ants were fed on dead insects, insect larvee, 
sugar water, pieces of lean meat, and the yolk of egg. The queens 
began laying in December and January, and laid during the rest of 
the winter. Sometimes I allowed the eggs to accumulate in the nest 
until the first ones began to hatch and then killed the entire bunch, 
thus getting all stages. The egg periods varied, but averaged be- 
tween twenty-five and thirty days. Very often by the time the first 
eggs began to hatch there were from one hundred to two hundred 
eggs in the nest. Sometimes I removed the queen and a few work- 
ers to another nest and removed the eggs each day, placing them with 
other workers, in order to estimate the time. I found it a very diffi- 
cult matter to get the later egg-stages in this way because of the fact 
that the workers ate many of the eggs; but it was necessary to have 
the eggs with workers or with a queen in order to prevent their being 
attacked by fungi. In order to remove the eggs or the queen, the 
entire colony was first stupefied with cold. 

The eggs were killed and fixed in a saturated solution of mercuric 
chloride in 35% alcohol to which had been added 2% of glacial 
acetic acid. The solution was used at a temperature just below 
the boiling point. The eggs were then transferred to 70% alcohol, 
in which they were left until the following day, or later. While in 
70% alcohol the embryos were dissected out from the membranes 
surrounding them by means of fine dissecting needles. This could 
be accomplished, after a week or two of practice, with little difficulty. 
The embryos were then stained in toto in Grenacher’s alcoholic borax- 
carmine, Delafield’s or Ehrlich’s hematoxylin, or orange G, and then, 
after decolorizing, carried up through the various grades of alcohol 


43 


to some clearing agent. I always over-stained the material and then 
decolorized in acid alcohol. For the study of the entire embryo a 
rather faint stain is much the better; but for embryos that are to 
be sectioned, a heavier stain is desirable. 

For clearing I used xylol, cedar oil, and clove oil. The two 
latter I found cleared a little better than xylol, and were more de- 
sirable also because of the fact that they do not evaporate so rapidly. 
I kept the embryos in the clearing agent in a watch crystal; but for 
drawing and for the study of any particular embryo, I removed it 
to a microscope slide upon which I had built up a ring of cerasine 
to such a height that the depth of the cell formed was just a little 
greater than the thickness of the embryo. Then by moving the 
cover-glass the embryo could be made to assume any desired posi- 
tion. An embryo can be kept in such a cell for weeks at a time. For 
the study of certain structures I found it very desirable to cut the 
embryo in two and to remove all the enclosed yolk. The spiracular 
openings, for instance, I could not make out until I had resorted to 
this method. . 

For sectioning the earlier stages I did not remove the egg mem- 
branes. I found that by piercing the chorion and allowing the egg 
to remain in melted paraffine for from eight to twelve hours it sec- 
tioned very well. These eggs were all stained in toto in Ehrlich’s 
hematoxylin and then counterstained on the slide with orange G, 
by the use of a saturated solution in 95% alcohol. I found that by 
using this method I did not over-stain with the hematoxylin; that 
I got a much better stain than by staining on the slide; avoided 
the necessity of running the slides through the different grades 
of alcohol, and hence much danger of losing sections by washing 
them off; and saved a great deal of time. The orange G differen- 
tiated the yolk from the superficial layer of protoplasm or from the 
germ layers. The sections were cut with a Minot’s rotary microtome 
and mounted with Meyer’s albumen fixative. The drawings were 
made in outline with an Abbé camera lucida. 


THE EGG 


The egg of C. ferrugineus may be described as somewhat Para- 
meecium-shaped, with a blunt, narrow anterior end, and with its great- 
est transverse diameter about one third the distance forward from 
the posterior end. The length of the egg is about 1.4 mm. and the 
transverse diameter is about .5 mm. When the egg is laid the pos- 
terior end makes its appearance first. 


44 


There are two external membranes, the chorion and the vitelline 
membrane. ‘The chorion is made up of two membranes: an outer, 
or exochorion, and an inner, or endochorion. It is difficult to dis- 
tinguish these two layers in sections, but sometimes when the eggs 
are removed from the fixing agent to 70% alcohol the inner layer 
separates from the outer one in bubble-like areas, and the two can 
then be further separated by needles. ‘The vitelline membrane is 
somewhat thinner and much more delicate than the chorion. The 
former stains more heavily with hematoxylin, while the latter stains 
more heavily with orange G. I was not able to distinguish any 
structure that I could identify positively as a micropyle. Ganin 
(1869) states that there is a single micropyle at the posterior end of 
the egg. Blochmann (1884), states that a micropyle occurs at the 
animal pole or upper end of the egg. It is probable that he means 
by “animal pole” the posterior end of the egg, since he says that he 
found what he took to be the egg nucleus and the sperm nucleus at 
that end of the almost ripe ovarian egg. In the freshly laid egg the 
nuclei always occur at the posterior end. 

If a freshly laid egg be sectioned longitudinally, it will be found 
to present the appearance shown in Plate I, Fig. 1. On the outside 
is the chorion, which stains rather deeply with orange G; and inside 
the chorion, closely investing the protoplasm, is the vitelline mem- 
brane, which takes the hematoxylin stain. On the inside of the 
vitelline membrane is a comparatively thick layer of peripheral pro- 
toplasm, much thicker at the posterior than at the anterior end or 
at the sides. The part of this layer in the posterior one-third of the 
egg is noticeably different from that of the anterior two-thirds, that 
at the anterior end being much more vacuolated, with a tendency 
toward network formation, while that at the posterior end is almost 
devoid of vacuoles. Numerous small yolk granules are seen embedded 
in this protoplasmic layer, especially at the posterior end. In many 
places the small granules are found fitting into small pocket-like de- 
pressions. In other places the outer edges of these depressions, meet- 
ing, enclose the granules in vacuoles. This indicates the manner in 
which the yolk granules probably become embedded in the peripheral 
layer of protoplasm. 

Another respect in which the protoplasmic layer at the posterior 
end differs from that at the anterior end and at the sides is in the 
presence of an immense number of minute rod-like bodies which al- 
most completely fill the protoplasm at that end of the egg and stain 
readily with hematoxylin. Blochmann (’84, pp. 245-246) mentions 
finding these bodies in the ovarian eggs of Camponotus ligniperdis 


45 


and Formica fusca, but says that they disappear with the formation 
of the yolk in the egg. He found them later (’87 and ’92) in certain 
other insects, and similar bodies have since been found by Forbes 
(1892) in the cecal glands of various Heteroptera, and identified by 
him as bacteria, and by Wheeler (’80, p. 306) in the egg of Blatta 
germanica. Recently they have been proved to be bacteria by Mercier 
(07), who grew them in cultures. Those I found in C. herculeanus 
stain deeply with eosin and with methylene blue but do not take the 
Gram stain. So far as I know this is the first time these bacteria 
have been seen in ants’ eggs in this country. 

The peripheral layer of protoplasm at its inner edges passes out 
into what appears in sections as a delicate network of protoplasm 
which extends through the entire egg. This delicate network shows 
very clearly because of the fact that the protoplasm stains more 
strongly with hematoxylin while the yolk granules stain more 
strongly with orange G. Both protoplasm and yolk will take either 
stain, but the yolk stains much more readily with orange G, while 
the protoplasm stains much more readily with hematoxylin, thus 
preducing a very good differentiation. Near the posterior end of 
the egg, and to a less extent near the anterior end, this network leaves 
many large vacuoles between which occur yolk granules. Near the 
center of the egg the yolk granules are massed to such an extent that 
there are very few or no vacuoles. These yolk granules vary in size, 
and also somewhat in shape, but approach a globular form, and are 
very finely granular. They range in size from a diameter of about 
.0o0o5 mm. to a diameter of about .027 mm., with an average diameter 
of about .o18 mm. 

In the peripheral layer of protoplasm at the posterior end of a 
freshly laid egg, or of one at a somewhat later stage (one to thirteen 
hours), is found a very large, much vacuolated, heavily staining 
nucleus (Figures 1 and 2). In addition to this, there is found sit- 
uated very near the large one, in some of the eggs, a much smaller 
nucleus (Figures 1 and 3), having the same appearance as the large 
one except that it is generally denser, that is, less vacuolated. In 
one of my slides the two nuclei were just touching each other. In 
sections of several somewhat later stages, still more nuclei of exactly 
the same appearance were found. These nuclei all had the same 
appearance structurally. I did not see in those I examined any ap- 
pearance of karyokinetic figures. Of two eggs killed just after be- 
ing laid, one contained but the one large nucleus, the other contained 
the large nucleus and a small one. Of three eggs one hour old, one 
had only the one large nucleus, one had the large one and one small 


46 


one, and the other had the one large nucleus and two small ones. 
One egg four hours old showed but the one large nucleus. Of five 
eggs from one to four hours old, one had two nuclei, the large one 
and one small one; each of the other four had only the large nucleus. 
One egg, from one to twelve hours old, had but the one large nucleus. 

In an egg killed eight hours after laying, | found three nuclei, 
each about one third as large as the large ones mentioned above, and 
two smaller ones, all having the same characteristic vacuolated ap- 
pearance. All five were in the peripheral layer of protoplasm near 
the posterior end of the egg. In another egg eight hours old there 
was but the one large nucleus at the posterior end of the egg; but 
in addition to this, in the midst of the yolk at about one-third the 
distance from the anterior end, appeared a few small irregular stel- 
late nucleated masses of protoplasm, having exactly the same ap- 
pearance as the ones that appear successively more numerous in some- 
what later stages. In an egg eleven hours old, there was but the one 
large nucleus at the posterior end, and near the anterior end there 
were a few small irregular nucleated masses of protoplasm. In addi- 
tion to these, scattered throughout the yolk in the posterior half of 
the egg, were a number of small stellate masses of protoplasm, most 
of which had exactly the same appearance as those at the anterior 
end except for the fact that I could not see that they were nucleated. 
Some of them looked very much as though they were detached frag- 
ments of the large nucleus, having the same vacuolated appearance. 
The yolk is now changing its appearance, becoming liquefied, the 
yolk granules breaking dow n and the vacuoles increasing in size and 
awe Ina thirteen hour stage I found only the one large nucleus. 
In an egg twenty hours old I found one nucleus, very large and very 
irregular (Figure 4), at the posterior end in the usual position of 
the large nucleus. In addition to this, in the yolk occur a number of 
small, rather deeply staining, vacuolated masses that have the same 
appearance structurally as the large nucleus. They appear either to 
be made up entirely of cytoplasm or entirely of karyoplasm, that is, 
there is no part more deeply staining than the rest to indicate that 
they are nucleated masses of protoplasm. The large nucleus was 
.og mm. across, and the largest of the small masses was .025 mm. in 
diameter. In the anterior half there are scattered throughout the 
yolk near the center of the egg, a number (about twenty altogether) 
of stellate masses of protoplasm with small, globular, deeply-staining 
nuclei. These generally occur in pairs, indicating their origin by 
division. The conditions which are described above must be similar te 
those found by Weismann in Cyntpide. “According to Weismann, 


47 


in Rhodites and Biorhiza aptera (Cynipide) the first cleavage- 
nucleus divides at first into nuclei which shift apart in the direction 
of the longitudinal axis of the egg, and, according to their position, 
are known as the anterior and posterior “pole nuclei.” While the 
anterior nucleus remains inactive for some time, the posterior, by a 
kind of budding (?), gives rise to numerous nuclei, which take part 
in the formation of the blastoderm. ‘The anterior nucleus, on the 
contrary, after the completion of the blastoderm, is said to produce 
by division the nuclei of the so-called inner germ-cells or yolk-cells.’’* 
In the case of Camponotus, however, the anterior cells go to make 
up at least the greater part of the blastoderm. 

In the next stage I have, (marked one day old,) the nucleated 
masses of protoplasm are beginning to arrange themselves in a regu- 
lar layer in the yolk just a little distance in from the peripheral pro- 
toplasm (Figure 5). ‘This layer is more regular and the nuclei are 
more numerous in the anterior than in the posterior half of the egg; 
furthermore, the nuclei lie nearer the periphery. There are still a 
great many nuclei scattered indiscriminately through the central por- 
tion of the yolk. Division seems to be going on much more rapidly 
in the anterior half, and many karyokinetic figures can be seen, some- 
times six or eight in the same section. 

In a stage a few hours later the nuclei at the anterior end have 
migrated outward until they form a loose layer in the peripheral 
protoplasm. Towards the posterior end the nuclei do not divide so 
rapidly and do not reach the peripheral protoplasm as soon as at the 
anterior end, so that a longitudinal section of this stage has the ap- 
pearance shown in Plate II, Figure 6. Figure 7 shows a section 
through the peripheral layer of protoplasm at the anterior end parallel 
with the surface. 


FORMATION OF THE BLASTODERM 


By the time the nuclei have reached the periphery at the posterior 
end of the egg the layer of protoplasm in the anterior half has be- 
come divided by deep fissures, running in from the outside, into 
columnar cells, each cell containing one nucleus. The nucleus has 
in each case migrated outward to the extreme distal end of the cell. 
These cells are not formed, however, over the entire surface. They 
form a cap over the anterior end, and extend on the ventral surface, 
backward, about half-way to the posterior end. The dorsal half of 


*Quoted from Korschelt aud Heider (’99, p. 264). 


48 


the egg is still uncovered with cells. The nuclei here lie embedded 
in the peripheral protoplasm, which has become much thinner. There 
are still many nucleated stellate cells scattered throughout the yolk. 
This stage, which represents conditions at the beginning of the sec- 
ond day, is illustrated by Plate II, Figure 8. 

During the second day (PI. III, Fig. 9) cells are formed over the 
entire surface of the posterior half of the egg in the same way that 
they were formed over the ventral surface of the anterior half 
the first day. These cells differ from those at the anterior end in 
being much larger and broader. The protoplasm is mostly at the 
distal end of the cell, while the basal part contains an immense num- 
ber of yolk granules. At this stage those cells at the posterior end 
contain also a very large number of the bacteria mentioned above. 
The nuclei in these cells lie in the distal ends, as do those of the an- 
terior end, but they are not nearly so easily made out. On the ventral 
surface the cells of the posterior half meet those of the anterior half 
about half-way between the two poles to form a continuous layer. 
The transition from one type of cell to that of the other is not a 
gradual one but is rather abrupt. On the dorsal surface the layer 
of cells from the posterior end has grown forward about the same 
distance as on the ventral side, but the layer of cells from the an- 
terior end has not grown backward to meet it, so there is still a 
small area on the dorsal surface just back of the anterior end that 
is as yet not covered with cells. The protoplasmic layer has changed 
here until there is nothing but a thin membrane separating the yolk 
from the vitelline membrane (Fig. 10). 

The cells that were described above as being formed the first 
day on the ventral surface of the anterior half have changed de- 
cidedly in appearance. They have become longer and more columnar 
and taper somewhat at the base. This layer of cells forms the be- 
ginning of the germ band. At their proximal ends they merge into 
the protoplasm which has formed a layer lying between the yolk and 
the cells. In the posterior half this layer almost disappears in the 
protoplasmic network; but in the anterior half it is much heavier 
and really forms a syncitium, since it contains quite a number of 
nuclei. This syncitium seems to act as a kind of “feeder” to the 
layer of cells, since it is the seat of rapid nucleus formation, nuclei 
appearing here in various stages of mitosis, and since the nuclei be- 
ing formed here appear to migrate outward, drawing with them a 
part of the syncitial protoplasm, thus forming new cells. ‘These mi- 
grating nuclei can be found at the distal ends of the cells just form- 
ing in this way, anywhere between the protoplasmic layer and the 


49 


level of the distal ends of the mature cells. This view of the tunc- 
tion of the syncitial layer is further supported by the fact that in 
two places in this layer there are longitudinal thickenings containing 
many more nuclei extending from the anterior end backward as far 
as the end of the germ band, and these thickenings occur near the 
lateral edge of the germ band, or where there is greater need for 
rapid cell-formation. Furthermore, a larger number of the cells of 
the germ layers are connected at their bases with the syncitial thick- 
ening than with any other equal area of the layer. This is shown 
by Figure 10, which represents a cross-section through the posterior 
part of the germ band at this stage, that is, just a little in front of 
the middle of the blastoderm. It will be noticed that there are large 
blastoderm cells on the dorsal side, showing that here this layer has 
grown farther forward on the dorsal side than the point on the ven- 
tral side where the blastoderm cells meet the posterior end of the 
germ band, which in this stage is about the middle of the egg. Figure 
II represents a transverse section of the same egg taken farther for- 
ward, through the region where there is still a small area on the 
dorsal side that is not as yet covered by the blastoderm cells; the 
dorsal side of the section is limited, consequently, by the thin pro- 
toplasmic layer mentioned above. 

In Figures 9, 10, and 11, most of the cells, both of the germ band 
and of the blastoderm outside the germ band, are seen to contain 
a very large number of yolk granules which have passed through the 
protoplasmic layer into the bases of the cells. The large cells of the 
blastoderm especially are distended with the yolk granules, the amount 
of yolk in many cases being greater than the amount of protoplasm. 
At this stage many of the yolk granules have broken down, leaving a 
granular liquid mass. The stellate yolk cells have almost disap- 
peared, only a few being found scattered throughout the yolk mass. 
At the posterior end of the section shown in Figure g may be seena 
group of cells lying just inside the blastoderm which are smaller than 
the cells of the blastoderm. Also, in view of their later development, 
mention should here be made of certain cells in the posterior ventral 
part of the blastoderm which have become very greatly enlarged, 
and at their bases contain a large number of yolk granules. The 
protoplasm in these cells is denser than in those just at the end. One 
such cell is shown in Figure 9. 

An examination of the section shown in Figure 11, shows that 
the cells in the middle of the germ band at this point have taken on 
a different appearance from those at the sides. Instead of the narrow 
columnar cells with their nuclei out at their extreme distal ends 


30 


which appear at the sides, and also in the middle a few sections back 
of this point, there are more or less globular cells having their 
nuclei near their centers. They are undergoing rapid division, as 
is shown by the fact that a large number are seen in various stages 
of mitosis. These cells, including about the middle one-third of the 
germ band, are seen to be sunk below the level of the columnar cells 
on either side, forming a broad shallow depression. ‘This depression, 
which has been termed by some embryologists the middle plate, rep- 
resents an invagination from which will arise the mesoderm. At 
this stage the middle plate occurs only near the anterior end. 

In a stage a day later (three days old) the small area on the 
dorsal side that still remained uncovered by the blastoderm has become 
overgrown by the layer of cells, so that we now have the blastoderm 
and the germ band completely enclosing the yolk (Fig. 12). Sections 
through the egg at this stage show us that the cells of the blastoderm 
are not all alike. In the first place we have in the anterior half of 
the ventral surface, the germ band, the surface cells of which are 
columnar and stain deeply with hematoxylin (Fig. 12). Just pos- 
terior to the germ band comes a layer of large polygonal cells con- 
taining only a small amount of protoplasm in comparison with the 
large amount of yolk material within them. The protoplasm, which 
is rather dense, but does not stain so deeply as in the cells of the 
germ layer, is all together, while the yolk granules fill the rest of 
the cell. This layer extends almost to the posterior end, but just 
before that end is reached a few enormously enlarged cells occur 
which closely resemble those just described, but are conspicuous be- 
cause of their great size. They appear to be multinucleate, although 
their nuclei do not show up very well, and to enter into close relation- 
ship with the posterior end of the inner protoplasmic layer. They con- 
tain a number of vacuoles, and, like the cells just described, they 
contain a very large amount of yolk material, and their rather dense 
protoplasm stains more lightly than that in the cells of the germ 
band. At the posterior end, and extending forward from these al- 
most half the distance on the dorsal side, occurs a layer of rather 
large polygonal cells which contain only a few yolk granules. The 
protoplasm of these cells is less dense than that of the cells just de- 
scribed, but it takes a deeper stain, and hence these cells are very easily 
distinguished from the others. About half-way between the anterior 
and posterior ends, these cells give way to cells of the same kind 
as those which occur just posterior to the germ band on the ventral 
surfaces. These cells extend forward on the dorsal surface to meet 
the germ band at the anterior end of the blastoderm. 


ol 


At the anterior end of the germ band, a transverse depression, 
or invagination, occurs, beneath the floor of which there has devel- 
oped a large cell-mass composed of more or less circular cells having 
deeply staining nuclei. These cells represent a further development 
of the cells mentioned as occurring in the two-day stage below the 
middle plate. The middle plate at this stage, with its accompanying 
cells beneath, extends back a little farther than in the two-day stage. 

Just a little distance in front of the transverse depression, or 
invagination, the large cells which cover the anterior half of the 
dorsal part and extend to the anterior end of the blastoderm give 
way to a one-celled layer of somewhat flattened loosely-connected 
cells, which resemble the cells of the germ band in their structure and 
in the manner in which they stain. This layer, which at this stage 
extends backward only a very little way, not yet bridging the in- 
vagination, represents the beginning of the serosa. At the posterior 
end of the germ band also, there is a slight transverse groove, from 
the posterior border of which a few cells extend forward over the 
posterior end of the germ band. These cells, however, are not dif- 
ferent in character from those just posterior to them, that is, they 
have not changed their shape so as to form a layer of flattened cells 
similar to the one extending backward from the anterior end. At 
both the anterior and posterior ends the lateral edges of the germ 
band are sinking slightly below the level of the other cells so that 
both grooves are slightly crescentic, the horns of the anterior one 

extending backward, and these of the posterior one extending for- 
ward. 

The inner protoplasmic layer, which lies between the cells and the 
yolk mass, is very greatly thickened at the anterior end, where the 
greatest cell growth is taking place. The posterior end of this layer 
seems to have contracted somewhat, ending bluntly, and leaving 
a space between it and the posterior end of the blastoderm. 
Near the dorsal side the group of small cells, mentioned in the 
description of the two-day stage as lying just inside the posterior 
cells of the blastoderm, are seen to be applied to this blunt, posterior 
end of the inner protoplasmic layer, although they still retain a loose 
connection with the surface cells. The bacteria mentioned above 
can still be seen in the posterior cells. There are still a very few 
cells scattered throughout the yolk mass. 

In the sections I have representing the four-day stage there are 
few further changes of importance. The serosa has grown farther 
backward over the germ band, extending about half its length. Its 
anterior attachment has begun to retreat somewhat over the antero- 


52 


dorsal part of the blastoderm toward the posterior end, so that the 
anterior end of the blastoderm is now completely enclosed by the 
serosa. This retreating of the attachment of the amnion apparently 
takes place by a kind of progressive delamination from the blasto- 
derm cells successively farther back. ‘The anterior end of the germ 
band has retreated somewhat and the anterior cell-mass has in- 
creased in size. ‘The middle groove and the middle plate have grown 
farther backward but have not reached the posterior end of the germ 
band, while at the anterior end the surface is again even, the middle 
groove having grown over. ‘The transverse depression at the pos- 
terior end of the germ band has become somewhat deeper, but the 
blastoderm cells at the posterior edge of this depression have grown 
forward but little if any farther than in the last stage described. 

In a stage five days old (Pl. IV, Fig. 15), the serosa has grown 
backward on all sides almost to the posterior end of the blastoderm, 
enclosing the large cells of the blastoderm and the germ band. At 
the posterior end of the germ band the serosa did not unite with the 
forward-projecting cells from the posterior end of the transverse 
groove, but continued to grow on backward, enclosing those cells 
with the posterior end of the germ band. 

At the position of the transverse groove mentioned in preceding 
stages, the germ band dips downward and backward diagonally and 
then continues to grow toward the posterior end, following the thin 
layer of peripheral protoplasm. At this stage the backward growth 
from the lower end of the incline has proceeded only for the length 
of a few cells. From that point backward toward the posterior end 
of the blastoderm the layer of inner protoplasm, which although very 
thin is easily distinguishable, rises again toward the surface, leaving 
a very broad depression, in which lie a mass of large blastoderm cells 
covered by the serosa. 

At the anterior end the germ band turns upward and then back- 
ward again on the dorsal side, and since the dorsal and ventral parts 
are now connected by a layer of cells, this gives to the anterior end 
of the germ band the appearance of a closed tube with the lumen 
opening backwards. The layer of thin epithelial cells forming the 
dorsal surface of this tube extends backward at this stage, as a deli- 
cate layer, to about the level of the transverse groove near the pos- 
terior end of the germ band on the ventral side. From this point 
the wall of the tube, which widens somewhat here, extends backward 
as the inner protoplasmic layer to the posterior end of the blastoderm, 
where, with the same layer from the sides and the ventral surface, it 
forms the other closed end of the tube. Between the antero-dorsal 


53 


surface of this tube and the serosa lies a mass of cells in an irregular 
layer, of the same nature as those lying in the hollow on the ventral 
surface. The axis of the rounded, tube-like, anterior portion of the 
germ band does not coincide with the longitudinal axis of the entire 
egg, but is anteriorly inclined towards the ventral surface. The hol- 
lows on the dorsal and ventral surfaces give to the germ band and 
the inner protoplasmic layer a somewhat slipper-shaped appearance 
in longitudinal vertical sections, the heel being formed by the germ 
band and the toe by the inner iayer of peripheral protoplasm, the 
longitudinal axis of the slipper lying diagonal to the longitudinal 
axis of the egg. Encircling the toe of the slipper and extending for- 
ward on the dorsal surface about half the length of the blastoderm 
are the rather deeply-staining cells mentioned as occurring in this 
position in the three-day stage, but the layer has pushed forward 
farther on the dorsal side at this stage. Most of these cells contain 
the bacteria mentioned above. At the anterior end of this layer on 
the ventral surface occur the large vacuolated multinucleate cells 
described above. The group of cells originating at the anterior end 
of the ventral groove has increased greatly in size so that the anterior 
end of the germ band now appears as a solid mass of cells. The 
ventral groove and the cells of the middle plate have just about 
reached the posterior end of the germ band. 

At the age of six days the germ band has grown backward on 
the ventral side along the inner layer of peripheral protoplasm to 
the most posterior place occupied by that layer in the region of the 
middle of the egg near the posterior end (Fig. 16). It has grown 
back as a layer several cells in thickness in the median line, thinning 
out to a delicate one-celled layer laterally. Over the anterior half 
this layer is continuous with the delicate one-celled layer extending 
backward from the antero-dorsal part of the germ band, forming here 
a dorsal closure of the embryo. This dorsal closure has not yet been 
effected over the posterior part. The layer of inner peripheral pro- 
toplasm now contains a great many more nuclei, so that it forms a 
loose nucleated layer extending over the entire dorsal area and lying 
just inside the delicate one-celled layer which is continuous with the 
edges of the germ band. 

’ At the very posterior end of the germ band a significant change 
is beginning at this stage. The germ band now extends back to 
the point where the peculiar, large, multinucleate cells and the large 
heavily-staining cells, mentioned as occurring at the posterior and 
the postero-dorsal part of the blastoderm, begin. At this point the 
germ band forms a knot-like thickening, and from this thickening 


34 


there extend several finger-like processes composed of the small germ- 
band type of cells. These finger-like processes work themselves in 
between the large blastoderm cells, tending to enclose them in meshes. 
The significance of this process will be seen in later stages. 

The embryo, as it may now be called, has shortened somewhat 
in length and at the same time has increased in circumference, so that 
the large blastoderm cells mentioned in the five-day stage as occurring 
in hollows on the dorsal and ventral sides of the germ band have 
been crowded out of these positions, those on the dorsal side being 
forced into the anterior end of the egg, and those on the ventral 
side now occupying the postero-ventral part of the egg. These cells 
contain a great deal of yolk and are evidently absorbed as food, since 
they gradually disappear in later stages. The ventral side of the 
embryo now lies next to the vitelline membrane, and the dorsal side 
is separated from the vitelline membrane by only the single layer of 
the large heavily-staining blastoderm cells, which now extend well 
towards the anterior end of the embryo, and which at the posterior 
end are beginning to be enclosed by the finger-like processes from 
the posterior end of the embryo. 

In an eight-days stage (Fig. 17) the small cells which originally 
grew out as finger-like processes from the posterior end of the germ 
band have increased in number to such an extent that they now enclose 
all the large heavily-staining blastoderm cells mentioned above and 
the large multinucleate cells in a perfect meshwork, extending as far 
forward dorsally and laterally as the large cells extend, that is, al- 
most to the anterior end of the embryo. At the posterior end these 
large cells are in a group which becomes thinner as it extends for- 
ward, until near the anterior end it becomes a layer one-celled in 
thickness. This group ends posteriorly with the large multinucleate 
cells. The cells forming the network are very small, but are easily de- 
tected by the presence of the deeply-staining nuclei. At the posterior 
end of the embryo where the germ band broke up into the finger- 
like processes consisting of the small cells, the outermost of these 
processes, which is now a very thin, delicate membrane, extends back- 
ward over the large multinucleate cells, and enclosing the group of 
large heavily-staining cells continues forward to meet the thin layer 
extending backward on the dorsal side of the embryo, thus forming 
the dorsal closure, and thus including, as a part of the embryo, the 
large cells which originated in an entirely different part of the blasto- 
derm from that which formed the original germ band (PI. III, Fig. 
9g). ‘The inner layer of peripheral protoplasm lies just beneath this 
network, thus enclosing it between two membranes. This inner layer 


D5 


has, scattered through it, very large and heavily-staining nuclei. One 
of these nuclei is shown in the figure situated at the anterior end and 
another at the posterior end, in very noticeable thickenings of the 
layer. The nuclei of the serosa have increased greatly in size and 
are now very conspicuous, lying just beneath the vitelline membrane. 

The serosa is the only embryonic membrane that develops in the 
case of Camponotus to enclose the embryo entirely. This develops, 
as has been seen, by a backward growth as a single layer from the 
anterior border of the cephalic groove. At the posterior end of the 
germ band it does not unite with the posterior edge of the caudal 
groove, but grows on backward to enclose the rest of the blastoderm. 
This differs from the typical method of formation of embryonic 
membranes in two ways: (1) the entire membrane is formed by a 
growth from the cephalic fold, the caudal fold being rudimentary ; 
(2) the growth occurs as a single and not as a double layer. There 
is, therefore, no amnion formed over the ventral surface of the 
embryo. The dorsal closure, however, has been effected, as has been 
described, by a delicate one-celled layer which is continuous with 
the edges of the germ band. ‘This layer is similar in structure to 
the serosa. It grows out from the edges of the germ band, spreads 
dorsally, and closes over to form the dorsal body-wall of the em- 
bryo; hence it is to be regarded as the amnion. 

Graber has shown (’88, pp. 144-146) that there are two em- 
bryonic membranes in Polistes gallica, Formica rufa, and Hylotoma 
berberidis. He says that the inner layer becomes closely applied to 
the germ band and is indistinguishable from the latter. In Campono- 
tus | have been unable to find more than. the one layer on the ventral 
side of the embryo. Carriere (’97, pp. 396) found but the one layer 
in Polistes gallica and Chalicodoma muraria, and Biitschli (1870) 
found but one in Apis. Ganin, who studied the development of sey- 
eral species of Formica and Myrmica, also says that there is but one 
embryonic layer. 

The ventral part of the embryo, which is in the position of the 
original germ band, is now much narrower than the original germ- 
band and is in the form of a narrow ridge-like thickening along the 
median ventral line, widening out at the anterior, and, to a less ex- 
tent, at the posterior end. Figure 18, Plate V, represents a cross- 
section of this stage showing the ridge-like thickening on the ventral 
side, and the large cells forming a layer extending about half-way 
around on the ventral side. The anterior widening shows the funda- 
ments of appendages and of the stomodzal invagination, but the 
proctodzal invagination does not appear until several days later. 


56 


In an embryo ten days old the ventral thickening widens some- 
what and the large dorsal cells have pushed farther around towards 
the ventral side. This process continues in succeeding stages, and in 
a cross-section of an embryo at the age of fourteen days we have 
the appearance shown in Figure 19. Here the ventral thickening has 
become wider and somewhat thinner and is composed of two layers: 
an outer, compact ectodermal layer; and an inner, somewhat looser 
layer of mesodermal cells. The large cells from the dorsal side have 
grown around a little farther toward the ventral side. ‘These cells, 
together with the small cells which form a network among them, 
form a layer which is beginning to separate slightly from the thin 
ectoderm dorsally and laterally, leaving a small space occupied by 
scattered cells. The invagination of the proctodeum has not yet 
developed at this stage. 

In a somewhat later stage, represented by Figure 20, (the exact 
age of these later stages can not be given,) the ventral thickening has 
widened somewhat, and in the middle of this thickening there are 
two longitudinal elevations, inside of which we see the beginnings of 
the nerve cord. ‘These appear in cross-section as two circular areas 
of cells overgrown with the ectoderm. The layer of mesoderm cells 
which we found lying just below the ectodermal thickening in the 
fourteen-day stage has here split into two parts, one part lying on 
each side of the developing nerve cord. 

The layer of large cells which has been growing around from 
the dorsal side has now reached the median ventral line, and the two 
edges unite to form a circular layer. The ultimate fate of these cells 
is now evident. They, together with the network of small cells which 
grew out from the posterior end of the germ band, and with the 
scattered cells of the inner layer of peripheral protoplasm, have 
formed the mesenteron. ‘These cells which were enclosed in the 
network and were originally very large, are now much smaller, and 
there is no longer a clear distinction between the various kinds of 
cells which went to make up the layer. The mesenteron has now 
completely separated from the surface ectoderm, leaving a well-de- 
veloped body cavity. 

The mesenteron ends blindly at both ends. Its shape may be 
seen from Figures 22 and 24. Its wall is thick, appearing in sections 
as a protoplasmic network enclosing the cells. This network is es- 
pecially noticeable on the inner border. 

By this time, appendages have been formed and the invaginations 
of the stomodzeum and proctodzum are well developed. The de- 
velopment of the appendages and the further development of the 


57 


alimentary canal and of the nervous system will be given on the fol- 
lowing pages. 


THE DEVELOPMENT OF THE EXTERNAL FORM 


Figure 21, Plate V, represents an embryo about twelve to four- 
teen days old. The embryo occupies a position somewhat nearer the 
posterior than the anterior end of the egg, with a mass of large, 
faintly-staining cells at each end. ‘The serosa encloses these cells 
with the embryo. The ventral thickening appears as a ridge along 
the median ventral line, curving around at each end in the form of 
a-large letter C. At the anterior end there is a slight widening of 
this ridge which indicates the beginnings of the procephalic lobes. 
At the posterior end the thickening passes insensibly into the darker 
posterior dorsal portion of the embryo. This is due to the fact, as 
we have noticed in the sections, that the posterior end of the original 
germ-band breaks up into finger-like masses of small cells which 
form a network around the large heavily-staining cells of the posterior 
end of the blastoderm. A very slight indication of segmentation has 
already made its appearance, due to the beginning of the formation 
of the ganglia of the ventral nerve-chain, the thickenings of which 
may be seen in lightly stained embryos. Sections of this stage show 
that the invagination of the stomodzum has just begun, but there is 
no indication of it as one looks at the entire embryo. The invagin- 
ation of the proctodzum has not yet begun. 

Figures 22 and 25 represent a stage in which the layer of cells 
from the inner posterior dorsal part of the embryo has grown around 
to the ventral side along its entire length, thus completing the mesen- 
teron, which now has the appearance of a pear-shaped sac, closed at 
both ends, the small end being the anterior one. This pear-shaped 
sac enclosing the yolk almost fills the embryo, though a small space 
is noticeable between it and the outer layer or ectoderm, this space 
representing the body cavity. At the anterior end of the embryo 
there is a well-developed, thick-walled, backward-projecting, U-shaped 
invagination of the outer ectoderm which represents the stomodzum. 
The posterior end of the stomodzum almost reaches the anterior 
end of the mesenteron. The invagination of the proctodetm is also 
well-developed at this stage. At the anterior end of the embryo at 
this stage the appendages are already well formed. Just in front 
of the stomodeum is a median evagination of the ectoderm pro- 
jecting anteriorly and dorsally, which when viewed from the side 
appears as a pear-shaped body, but when viewed from a_ postero- 


58 


dorsal direction appears as a narrow oblong with its greatest length 
extending transversely to the long axis of the embryo. ‘This is the 
fundament of the labrum. On each side of the labrum is a wide 
lobe-like thickening of the ectoderm, the two constituting the pro- 
cephalic lobes, and on each side of these is a small knob-like thicken- 
ing, representing the antenne. The antenne are not so well-devel- 
oped as in Myrmica (see Pl. VIII, Fig. 33). The fundaments of 
the antennze were noted by Ganin (’69), but he did not know what 
they represented. He says: ‘Es muss hier noch bemerkt werden dass 
man in solchen Entwicklungs-stadium auf den Seitentheilen jedes 
Kopflappens ein besonders rundliches Hockerchen beobachten kann; 
ubrigens existiren diese Hockerchen nur kurze Zeit und haben keine 
definitive Bedeutung; in den spateren Entwicklungsstadien kann man 
sie nicht mehr unterscheiden.” Wheeler (1910, p. 72) mentions the 
presence of traces of the antenne in the embryo of Formica gnava. 

Back of the stomodzum occur three pairs of lobe-like evagina- 
tions, the fundaments of the mandibles, maxilla, and labium  re- 
spectively. On the three following segments occur three similar lobe- 
like thickenings which are somewhat smaller than those representing 
the mouth parts. ‘These represent the three pairs of thoracic legs. 
Back of the thoracic segments occur ten other segments, upon which 
occur very small paired tubercles representing abdominal append- 
ages. On each side of the second thoracic segment occurs an irregular 
slit-like opening, the first thoracic spiracle. A pair of such openings oc- 
curs on the last thoracic segment and one on each of the following 
ten abdominal segments. Figure 23, Plate VI, represents a slightly 
older stage than Figure 22, Plate V. The dorsal part of the em- 
bryo has been removed, the yolk taken away, and the ventral part of 
the embryo straightened out to show all the segments. This corre- 
sponds to the stage of Formica gnava figured by Wheeler (1910, 
pp. 69). At this stage the ventral thickening extends almost half- 
way around to the dorsal side. 

Figure 24 represents a later stage, in which the embryo has 
straightened, the mouth parts extending directly forward instead of 
ventral as in Figure 22. The mesenteron is smaller, and shows as 
a regular oval in the middle of the body. Its ends are in contact 
with the now more fully developed stomodeum and _ proctodeum, 
although communication between the two has not yet been estab- 
lished. The stomodzeum extends backward as a narrow tube, while 
the proctodeum is a much shorter, somewhat oval sac. 

The posterior border of the head is indicated by a constriction, 
but there is no differentiation between thorax and abdomen at this 


09 


stage. The mouth parts are grouped nearer together and tend to 
bend in over the opening of the stomodzeum. The two lobes repre- 
senting the labium have grown together at their bases, making one 
plate. The small knobs representing the antennz are still present, 
but are very inconspicuous. The papille representing the thoracic 
legs and the abdominal appendages have now disappeared. 

The ganglia can be distinguished easily in faintly stained speci- 
mens at this stage. There is a double chain of ten abdominal ganglia, 
the last three of which are united in a compound ganglion in which 
the three constituent ganglia are easily distinguishable by their 
faintly-staining central portions. ‘The double chain is continued in 
the thorax as three separate pairs of ganglia, the anterior one of 
which connects with the subcesophageal ganglion, which is easily 
seen to be made up of three united pairs of ganglia. The sub- 
cesophageal ganglion is connected with the supracesophageal ganglion 
by a pair of commissures as usual. 

Figure 25 represents an embryo at just about the time of hatch- 
ing. It has practically the form of the young larva. The mesenteron 
has the same form as in the preceding stage except that its anterior 
end has narrowed considerably, giving it somewhat the appearance 
of the neck of a bottle. This neck is open at the anterior end, and 
encloses the posterior end of the stomodeum which is now open 
also, thus forming the valve-like connection between the stomodzum 
and the mesenteron. The proctodzeum has changed considerably in 
shape. It has a middle portion which is wide and bladder-like, from 
the posterior end of which a narrow tube-like part leads back to the 
anus, and from the anterior end of which a short narrow part passes 
forward to end blindly against the posterior end of the mesenteron, 
the connection between these two divisions of the alimentary canal 
not yet having been formed. 

The mouth parts are practically the same as in the larva, and the 
antenne have disappeared. The nerve cord presents practically the 
same appearance as in the preceding stage except that the last three 
abdominal ganglia and the three parts of the subcesophageal ganglion 
are more closely united. 


THE DEVELOPMENT OF THE EXTERNAL FORM OF THE EMBRYO OF 
Myrmica scabrinodis Ny]. 


Since a colony of Myrmuca scabrinodis var. sabuleti which I had 
in the laboratory was yielding an abundance of eggs while I was 
waiting for my Camponotus queen to begin laying, I decided to 


60 


make a study of the development of the external form of the em- 
bryo of that species. 

The eggs were killed and fixed in the same manner as has been 
described for the eggs of Camponotus. The eggs of Myrmica are 
much smaller than those of Camponotus, their greatest diameter be- 
ing about .45 mm. and their shortest diameter being about .35 mm. 
They may be described as broadly ovate in form, with one end slightly 
smaller than the other. As in the eggs of Camponotus, there are 
two external membranes, the chorion and the vitelline membrane, the 
chorion being composed of two layers—ectochorion and endochorion. 

The appearance of the first differentiation of the germ band from 
the undifferentiated blastoderm may be described as follows. At 
the anterior pole occur two somewhat oval-shaped thickenings of the 
blastoderm lying side by side with a clear area between them. These 
thickenings are slightly raised above the surrounding blastoderm. The 
edges facing each other are nearly straight, sometimes concave, while 
the outer edges are convex. At the opposite pole is a more or less 
circular denser area surrounded by a clear ring. This clear ring is 
connected by a light streak with the clear space between the two 
thickenings at the anterior pole. On each side of this light streak, a 
slight thickening of the blastoderm indicates the beginning of the 
germ band. The two oval thickenings at the anterior pole are the 
procephalic lobes. 

Figure 26, Plate VI, represents an early stage in which the em- 
bryo is curved around the yolk mass in the form of a capital C. 
There are slight indications of segmentation. The anterior end is 
thicker and wider than the posterior end, indicating the earlier de- 
velopment of the head region. The anterior and posterior ends are 
seen to be connected by the undifferentiated blastoderm. 

Figure 27, Plate VII, represents a later stage, in which the body 
segments are clearly indicated. The anterior and posterior ends, 
both of which are thickened, the anterior much more than the pos- 
terior, more closely approach each other, and the layer connecting the 
two ends has a large knob-like thickening near its middle. This 
thickening is composed of a large irregular mass of cells, and seems 
to be caused by a crowding and pushing outward of the cells of the 
layer connecting the two ends, as these ends approach each other. 
This layer continues at the sides, covering the yolk, and connects 
ventrally with the edges of the germ band. From a direct dorsal 
view this thickening is seen to be made up of two parts, separated 
laterally. This would naturally be the case if the thickening were 
caused in the way that has been suggested, that is, by the coming 


61 


together of the anterior and posterior ends of the embryo and by 
_ the dorsal growth of the sides of the germ band. 

The germ band has widened considerably, and now covers most 
of the ventral surface of the yolk. Figure 28 represents a view of 
the anterior end of the germ band at this stage, showing the pro- 
cephalic lobes in front, the beginning of the evaginations represent- 
ing the mandibles, maxille, and labium. At this stage there are 
only the faintest traces of the three pairs of thoracic appendages, 
and the invagination of the proctodzeum has not yet begun. 

In the stage represented by Figure 29, the curvature of the embryo 
is still greater, the anterior and posterior ends more closely approxi- 
mating each other. The dorsal thickening between the anterior and 
posterior ends is present as before, and as a rule is somewhat larger 
than in the preceding stage. The segments are much more clearly 
differentiated, there being ten abdominal segments. The procephalic 
lobes have increased in size, and the lateral edges of the germ band 
have grown farther dorsally. The labrum is shown in Figure 30, 
which represents a dorso-frontal view of the same stage. Figure 
30 shows also the extent of the invagination of the stomodzeum and 
the lobe-like appendages representing the three pairs of mouth parts 
and the first two pairs of legs. Figure 31, which represents a slightly 
different view of the same stage, shows also the last two pairs of 
thoracic appendages and the first pair of abdominal appendages, 
and on these segments also appear the first three pairs of spiracles. 
The invagination of the proctodzeum is shown at the posterior end. 

Figure 32, Plate VIII, represents a later stage, in which the 
labrum is well developed, pushing out in front of the invagination 
of the stomodzum, which has pushed farther inward. In fact, the 
posterior border of the labrum is continued inward to form the an- 
terior wall of the invagination. The procephalic lobes are larger and 
the germ band has grown farther over the yolk. The proctodeeum 
now appears as a distinct U-shaped thick-walled invagination. The 
dorsal thickening, made up of a cluster of cells, has disappeared in 
this stage. In stages just a little earlier than this, a constriction de- 
velops at the base of this thickening. This fact, together with the 
fact that in such stages the thickening is very easily broken away 
from its attachment as the embryo is moved about in the clearing 
agent, leads me to believe that it takes no part in the development of 
the embryo. ‘The membrane covering the yolk, from which this 
cluster of cells is formed, is homologous with what we have called 
the amnion in Camponotus. This cluster of cells, then, seems to 
correspond with the so-called amniotic dorsal organ which Wheeler 


62 


has described as occurring in Doryphora (Wheeler ’89, pp. 356-358), 
but sections of the embryo at this stage do not show anything that 
would lead me to believe that it is absorbed into the yolk. ‘The ab- 
sence of such a structure in Camponotus illustrates one striking dif- 
ference between the development in that genus and in Myrmuica. In 
Camponotus the amnion becomes the dorsal body-wall. 

At this age the segments are more deeply constricted off from 
each other. ‘The three pairs of mouth parts are further developed, 
and the thoracic and abdominal appendages are present, although in 
a side view it is difficult to distinguish them from the body segments. 

In the stage represented by Figure 33, the embryo is seen to be 
straightening somewhat, the posterior and anterior ends being farther 
apart. ‘The segments are still more deeply constricted off from each 
other, and the lateral edges of the germ band have grown dorsad 
until they have almost completed the dorsal closure. ‘The invagina- 
tion of the stomodeum has grown farther inward, the posterior 
end of the stomodzum almost reaching the yolk. On the sides of 
the procephalic lobes appear the small tubercle-like thickenings which 
represent the antenne. The labrum and the three pairs of mouth 
parts more closely approximate each other and tend to bend in over 
the opening of the stomodeum. This is shown better in Figure 34, 
which represents a frontal view of the same stage. 

In the stage represented by Figure 35, the embryo has straight- 
ened still more, and the dorsal closure has been completed. The 
mouth parts still more closely approximate each other and bend in 
over the stomodeum. The thoracic and abdominal appendages have 
disappeared, as have also the antenne. The stomodaum and procto- 
deum extend inward as far as the yolk, which is now enclosed in 
the somewhat pear-shaped mesenteron. The ventral segments are 
constricted off into blocks, three pairs in the thorax and seven in 
the abdomen, the last three abdominal segments having united to- 
gether. In each of these segments a primitive ganglion is evident, 
and in the last abdominal segment three ganglia appear, showing the 
compound nature of the segment. In the head region three separate 
ganglia can be distinguished, for the subcesophageal ganglion appears 
in the whole embryo to be all in one part. 

Figure 36 represents a stage just before the egg hatches, when the 
embryo has practically the form of the young larva. The embryo 
has now bent completely over so that the flexure, instead of being 
on the dorsal side as before, is on the ventral side. The thoracic 
region has lengthened considerably. The mouth parts are in their 
normal position for the larva and have practically the same form. 


63 


The stomodeum is discernible as a long narrow tube leading back 
to the mesenteron and connecting with it at about the level of the 
third thoracic segment. The connection is of the same valve-like 
character as has been described for the similar stage in the embryo 
of Camponotus. The proctodeum also is similar to that described 
for the corresponding stage of Camponotus. ‘There is a wide middle 
part connected at one end by a short, narrow, tube-like part with the 
anus and similarly, at the other end, with the posterior end of the 
mesenteron. The connection between the proctodeum and _ the 
mesenteron has not yet been established. The segmentation is es- 
sentially as in the preceding stage; the last three abdominal ganglia 
and the three ganglia composing the subcesophageal ganglion are 
more closely united, however, and the supracesophageal ganglion is 
larger than in the preceding stage. 


64 


LITERATURE TCI ED 


Bethe. Ay 

1902. Die Heimkehrfahigkeit der Ameisen und Bienen zum 
Teil nach neuen Versuchen. Biol. Centralb., Vol. 22, pp. 193- 
215, 234-238. 

Blochmann, F. 

1884. Ueber eine Metamorphose der Kerne in den Ovarialeiern 
und uber den Beginn der Blastodermbildung bei den Ameisen. 
Verhand. naturh.-med. Vereins Heidelberg, N. F., Bd. 3, pp. 
243-247. 

1892. Uber das Vorkomen von bakterienahnlichen Gebilden in 
Geweben und Ejiern Verschiedener Insekten. Centralbl. f. 
Bakteriol. u. Parasitenk., Bd. 11, p. 234. 

Butschh, O. 

1870. Zur Entwicklungsgeschichte der Biene. Zeitschr. f. Wiss. 

Zool., Bd. 20. 
Carriere, Justus. 

1897. Die Entwicklungsgeschichte der Mauerbiene (Chalicodoma 

muraria, Fabr.) im ei hrsg. von Otto Birger. Halle. 
Fielde, A. M. 

tool. ‘Hurther study: of an ant. Proce Acad. Nat. scr.) Pinlay 
Vol. 53, pp. 425-429. 

1904. Portable ant-nests. Biol. Bull., Vol. 7, pp. 215-220. 

1905. Observations on the progeny of virgin ants. Biol. Bull., 
Vol. 9, pp. 355-360. 

Forbes, S. A. 

1891. Bacteria normal to digestive organs of Hemiptera. Bull. 
Ii, State Lab. Nat: Hust. Voliy spp. u-7. 

1908. Habits and behavior of the corn-field ant, Lasius niger 
var. americanus. Bull. Ill. Agr. Exper. Sta., No. 131; also 
in 25th Rep. State Ent. Ill, pp. 27-40. 

Ganin, M. ; 

1869. Uber die Embryonalhtlle der Hymenopteren- und Lepi- 
dopteren-Embryonen. Mémoirs de L Académie Impériale des 
Sciences de St. Petersbourg, VII® Série, Tome 14, No. 5- 

Graber, V. 

T&888. Vergleichende Studien tiber die Kiemhullen und die Ruck 
enbildung der Insecten. Denkschr. Acad. Wiss. Wien., Bd. 
55, Pp. 109-158. 


Korschelt and Heider. 
1899. ‘Textbook of embryology of the invertebrates. 


Mercier, L. 
1907. Recherches sur les bactéroides des Blattides. Archiv. fur 
Protistenkunde, Bd. 9, pp. 346-356. 
Tanquary, M. C. 
Igti. Experiments on the adoption of Lasius, Formica, and 
Polyergus queens by colonies of alien species. Biol. Bull., 
Vol. 20, No. 5, Apr., 1911, pp, 281-308. 
Wheeler, W. M. 
1889. The embryology of Blatta germanica and Doryphora 
decemlineata. Journal of Morphology, Vol. 3, pp. 291-386. 
1903. The origin of female and worker ants from the eggs of 
parthenogenetic workers. Science, N. S., Vol. 18, pp. 830- 
833. 
1906. On the founding of colonies of queen ants, with special 
reference to the parasitic and slave-making species. Bull. Am. 
Mus- Nat.) Hist.,. Vol. 22; Art..4, pps 33-105. 
1910. Ants, their structure, development, and behavior. 


66 


EXPLANATION OF PLATES 


ABBREVIATIONS 


a., amnion 

Ia., 1st abdominal appendage. 
Ia.s., 1st abdominal segment. 
a.d.o., amniotic dorsal organ. 

an , anus. 

ant., antenna. 

b., blastoderm cells. 

b.c., body cavity. 

ca.g., caudal groove. 

c.c., Cleavage cells. 

c.g., cephalic groove. 

ch., chorion. 

c.n., cells forming network around 
large blastoderm cells. 

co.g., compound ganglion. - 

d.p., dense particles of protoplasm or 
nucleoplasm, possibly derived 
from cleavage nucleus. 

ec., ectoderm. 

e.g.b., lateral edge of germ band. 

f.c., large cells external to the em- 
bryo and surrounded by the 
serosa. Absorbed as food. 

g., fundament of ganglion. 

g.b., germ band. 

i.p.,inner peripheral protoplasm. 

k.c., group of small cells applied to 
the posterior end of the inner 
peripheral protoplasm. 

L., labrum. 
la., labium. 
L.b., large blastoderm cells. 


l.c., large polynucleate cells of the 
blastoderm. 
l.g., lateral groove. 
m., mandible. 
me., mesoderm. 
mes., mesenteron. 
mo., mouth. 
mx., maxilla. 
m.p., middle plate. 
n., Cleavage nucleus. 
nu., nuclei of the cells. 
p., proctodzeum. 
p.l., procephalic lobes. 
p.n., protoplasmic network. 
p.p., peripheral protoplasm. 
r.m.,remains of large nucleus. 
S., serosa. 
S.c., scattered cells of the body cav- 
ity. 
sp., spiracle. 
st., stomodzum. 
su., supracesophageal ganglion. 
sub., subcesophageal ganglion. 
t., thickenings of the inner layer of 
peripheral protoplasm. 
It., lst thoracic appendage. 
It.s., lst thoracic segment. 
v., vacnole. 
v.m., vitelline membrane. 
y., yolk mass. 
y.c., so-called yolk cells. 
y.g., yolk granules. 


PLATE I 
Fic. 1. Longitudinal section through the egg of Camponotus 1 hour old. X 52. 
Fic. 2. Large nucleus found in posterior end of egg of Camponotus 1 hour old. 
<a), 
Fic. 3. Small nucleus found in posterior end of egg of Camponotus 1 hour old. 
x 405. 
Fic. 4. Longitudinal section through egg of Camponotus 20 hours old, chorion 
removed. 52. 
Fic. 5. Longitudinal section through egg of Camponotus 1 day old. X 32. 
PLATE IT 
Fic. 6. Longitudinal section through egg of Camponotus a little older than the 
stage represented by Fig. 5. X 52. 
Fic. 7. Portion of a section taken through the layer of peripheral protoplasm of 
anterior end of egg of Camponotus. Same age as that represented by 
Fig. 6. X< 405. 
Fic. 8. Longitudinal section through egg of Camponotus 30 hours old. XX 52. 


Fic. 
Fic. 


Fic. 


Fic. 


Fic. 
Fic. 
Fic. 
Fic. 
Fic. 


Fic. 


Fic. 
Fic. 


Fic. 
Fie. 


Fic. 


Fia. 


Fic. 
Fic. 


Fic. 
Fic. 
Fic. 


Fic. : 
Fic. 


Fic. 
FIG. 
Fic. 
Fic. 
Fic. 


67 


PiateE III 


Longitudinal section through egg of Camponotus 2 days old. X 52. 

Transverse section through blastoderm near posterior end of germ band. 
Same age as the one represented by Fig. 9. X 78. 

Transverse section through same stage as that represented by Figs. 9 and 
10. Taken near anterior end of germ band.  X 78. 

Longitudinal section through blastoderm of Camponotus at a somewhat 
later stage than that represented by Fig. 9. > 52. 


PLATE IV 


Transverse section through anterior end of blastoderm of Camponotus. 
Same age as that represented by Fig. 12. X 78. 

Transverse section through middle of blastoderm. Same age as that 
represented by Fig. 12. 78. 

Longitudinal section through blastoderm of Camponotus 5 days old. 
xX 52. 

Longitudinal section through blastoderm of Camponotus 6 days old. 
aise 

Longitudinal section through blastoderm of Camponotus 8 days old. 
S< be: 

PLATE V 


Transverse section through blastoderm of Camponotus 8 days old. 
XLOS: 

Transverse section through embryo of Camponotus 14 days old. X 105. 

Transverse section through embryo of Camponotus 15-20 days old. 
x 105. 

Embryo of Camponotus 8-12 days old. X 52. 

Embryo of Camponotus showing development of appendages. 52. 


PLATE VI 


Ventral view of germ band of the same age as that represented by Fig. 
22. The yolk mass has been removed and the embryo, which is nor- 
mally curved over the yolk, has been straightened out. 52, 

Embryo of Camponotus. A later stage than that represented by Fig. 23. 
ioe: 

Embryo of Camponotus at a stage just before hatching. X 31. 

Embryo of Myrmica. Early stage. X 91. 


PLaTE VII 


Embryo of Myrmica, at a stage somewhat later than that represented by 
Bice 265 a <e 

Ventral view of anterior end of germ band of same age as that repre- 
sented by Fig. 27. X 91. 

Side view of later stage of embryo of Myrmica than that shown in Fig. 
Die ee OL, 

Ventral view of same stage as the embryo shown in Fig. 29. 91. 

A slightly different view of the same embryo. X 91. 


PLATE VIII 


A later stage of the embryo of Myrmica. X 91. 

A still later stage of the embryo of Myrmica. ‘91. 
Ventro-frontal view of same embryo as in Fig, 33. X 91. 
Embryo of Myrmica at a stage when it is straightening. X 80. 
Embryo of Myrmica just before hatching. X 91. 


eit iar) ee 


tg’ ew 


a, 


Beiep 


‘is 
A 


PLATE I 


OOS 


. 
fo) 
e 


Fic. 4 


II 


4 
4 
4 


Pratt 


KtGe0 


+ Oo 


Fr 


+; 6 


Fie 


ee aih 


Prats, TIL 


IV 


PLATE 


1S 


Fic. 


16 


cer 


Fic. 14 


15 


Fic. 


Pirate VI 


Fic. 26 


P| to 
ya) 


OT, 3 
nim es 


PratY VIL 


Fic. 30 


BiG et 


Fic. 2& 


Fic. 29 


PLATE VIII 


Fic. 33 


Fic. 34 


res 35 


NA 


084232 


